398 lines
9.7 KiB
C
398 lines
9.7 KiB
C
/*
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* Automatic primitive rasterization precision test.
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*
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* Draw prims at various sub-pixel offsets and examine where the quad is
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* actually drawn.
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* Check if the range of offsets which paint the right pixels falls within
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* OpenGL's specification.
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* In case of failures, report the coordinate bias needed to fix the problem.
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*
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* Note that even Mesa/swrast fails some line tests. This is because some
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* window coordinates wind up as 53.9999 instead of 54, for example. Enabling
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* the small translation factor below fixes that. Revisit someday...
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*
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* Brian Paul
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* 28 Feb 2008
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*/
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <GL/glew.h>
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#include <GL/glut.h>
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static int Width = 100, Height = 100;
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static int Win;
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static float Step = 0.125;
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#if 0
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/* This tiny offset fixes errors in Mesa/Xlib */
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static float Xtrans = 0.5 * 0.125;
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static float Ytrans = 0.5 * 0.125;
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#else
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static float Xtrans = 0.0;
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static float Ytrans = 0.0;
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#endif
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static void
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PointCalibrate(int xpos, int ypos)
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{
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GLfloat rgba[4];
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float x, y;
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float xmin, ymin, xmax, ymax;
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xmin = ymin = 1000.0;
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xmax = ymax = -1000.0;
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for (y = -1.0; y <= 1.0; y += Step) {
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for (x = -1.0; x <= 1.0; x += Step) {
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glClear(GL_COLOR_BUFFER_BIT);
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glBegin(GL_POINTS);
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glVertex2f(xpos + x, ypos + y);
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glEnd();
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glReadPixels(xpos, ypos, 1, 1, GL_RGBA, GL_FLOAT, rgba);
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if (rgba[0] == 1.0 && rgba[1] == 1.0 && rgba[2] == 1.0) {
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/* hit */
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if (x < xmin)
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xmin = x;
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if (y < ymin)
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ymin = y;
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if (x > xmax)
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xmax = x;
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if (y > ymax)
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ymax = y;
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}
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}
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}
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printf("Point at (%2d, %2d) drawn for x in [%6.3f, %6.3f] and y in [%6.3f, %6.3f]\n",
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xpos, ypos,
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xpos + xmin, xpos + xmax,
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ypos + ymin, ypos + ymax);
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if (xmax - xmin != 1.0 - Step) {
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printf(" => Inconsistant X-axis rasterization!\n");
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}
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if (ymax - ymin != 1.0 - Step) {
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printf(" => Inconsistant Y-axis rasterization!\n");
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}
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if (xmin < 0.0) {
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printf(" => Points should be X biased by about %f\n", xmin);
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}
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if (ymin < 0.0) {
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printf(" => Points should be Y biased by about %f\n", ymin);
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}
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if (xmax > 1.0) {
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printf(" => Points should be X biased by about %f\n", 1.0 - xmax);
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}
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if (ymax > 1.0) {
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printf(" => Points should be Y biased by about %f\n", 1.0 - ymax);
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}
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}
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/**
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* XXX Implement VLineCalibrate() someday
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*/
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static void
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HLineCalibrate(int xpos, int ypos, int len)
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{
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GLfloat rgba[2][4];
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float x, y;
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float ymin, ymax;
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float xmin_left, xmax_left, xmin_right, xmax_right;
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xmin_left = xmin_right = 1000.0;
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xmax_left = xmax_right = -1000.0;
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ymin = 1000;
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ymax = -1000.0;
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/*
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* First, check vertical positioning of the horizontal line
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*/
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for (y = -1.0; y <= 1.0; y += Step) {
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glClear(GL_COLOR_BUFFER_BIT);
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glBegin(GL_LINES);
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glVertex2f(xpos, ypos + y);
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glVertex2f(xpos + len, ypos + y);
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glEnd();
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glReadPixels(xpos + len / 2, ypos, 1, 1, GL_RGBA, GL_FLOAT, rgba);
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if (rgba[0][0] == 1.0) {
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/* hit */
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if (y < ymin)
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ymin = y;
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if (y > ymax)
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ymax = y;
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}
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}
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printf("H-line at Y=%2d drawn for y in [%6.3f, %6.3f]\n",
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ypos,
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ypos + ymin, ypos + ymax);
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if (ymax - ymin != 1.0 - Step) {
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printf(" => Inconsistant Y-axis rasterization!\n");
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}
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if (ymin > 0.5 ) {
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printf(" => Lines should be Y biased by about %f\n", ymin - 0.5);
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}
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if (ymax < 0.5 ) {
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printf(" => Lines should be Y biased by about %f\n", 0.5 - ymax);
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}
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/*
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* Second, check endpoints (for Y at 1/2 pixel)
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*/
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for (x = -1.0; x <= 1.0; x += Step) {
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glClear(GL_COLOR_BUFFER_BIT);
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glBegin(GL_LINES);
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glVertex2f(xpos + x, ypos + 0.5f);
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glVertex2f(xpos + x + len, ypos + 0.5f);
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glEnd();
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/* left end */
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glReadPixels(xpos - 1, ypos, 2, 1, GL_RGBA, GL_FLOAT, rgba);
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if (rgba[0][0] == 0.0 && rgba[1][0] == 1.0) {
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/* hit */
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if (x < xmin_left)
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xmin_left = x;
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if (x > xmax_left)
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xmax_left = x;
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}
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/* right end */
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glReadPixels(xpos + len - 1, ypos, 2, 1, GL_RGBA, GL_FLOAT, rgba);
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if (rgba[0][0] == 1.0 && rgba[1][0] == 0.0) {
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/* hit */
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if (x < xmin_right)
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xmin_right = x;
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if (x > xmax_right)
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xmax_right = x;
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}
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}
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printf("H-line [%d..%d) hit left end for x in [%6.3f, %6.3f] "
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"hit right end for x in [%6.3f, %6.3f]\n",
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xpos, xpos + len,
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xpos + xmin_left, xpos + xmax_left,
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xpos + len + xmin_right, xpos + len + xmax_right);
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if (xmax_left - xmin_left > 1.0 - Step) {
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printf(" => Inconsistant left-end rasterization!\n");
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}
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if (xmax_right - xmin_right > 1.0 - Step) {
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printf(" => Inconsistant right-end rasterization!\n");
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}
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if (xmin_left != xmin_right ||
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xmax_left != xmax_right) {
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printf(" => Inconsistant length!\n");
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}
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if (xmin_left < 0.0) {
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printf(" => Coords should be X biased by about %f\n", xmin_left );
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}
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if (xmin_right < 0.0) {
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printf(" => Coords should be X biased by about %f\n", xmin_right );
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}
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if (xmax_left >= 1.0) {
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printf(" => Coords should be X biased by about %f\n", -xmax_right + 1.0);
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}
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if (xmax_right >= 1.0) {
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printf(" => Coords should be X biased by about %f\n", -xmax_right + 1.0);
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}
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}
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static void
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QuadCalibrate(int xpos, int ypos, int width, int height)
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{
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GLfloat rgba1[2][4];
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GLfloat rgba2[2][4];
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float x, y;
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float xmin, ymin, xmax, ymax;
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xmin = ymin = 1000.0;
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xmax = ymax = -1000.0;
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for (y = -1.0; y <= 1.0; y += Step) {
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for (x = -1.0; x <= 1.0; x += Step) {
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glClear(GL_COLOR_BUFFER_BIT);
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glBegin(GL_QUADS);
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glVertex2f(xpos + x, ypos + y);
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glVertex2f(xpos + x + width, ypos + y);
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glVertex2f(xpos + x + width, ypos + y + height);
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glVertex2f(xpos + x, ypos + y + height);
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glEnd();
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/* horizontal measurement */
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glReadPixels(xpos - 1, ypos + 2, 2, 1, GL_RGBA, GL_FLOAT, rgba1);
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glReadPixels(xpos + width - 1, ypos + 2, 2, 1, GL_RGBA, GL_FLOAT, rgba2);
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if (rgba1[0][0] == 0.0 && rgba1[1][0] == 1.0 &&
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rgba2[0][0] == 1.0 && rgba2[1][0] == 0.0) {
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if (x < xmin)
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xmin = x;
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if (x > xmax)
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xmax = x;
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}
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/* vertical measurement */
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glReadPixels(xpos + 2, ypos - 1, 1, 2, GL_RGBA, GL_FLOAT, rgba1);
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glReadPixels(xpos + 2, ypos + height - 1, 1, 2, GL_RGBA, GL_FLOAT, rgba2);
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if (rgba1[0][0] == 0.0 && rgba1[1][0] == 1.0 &&
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rgba2[0][0] == 1.0 && rgba2[1][0] == 0.0) {
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if (y < ymin)
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ymin = y;
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if (y > ymax)
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ymax = y;
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}
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}
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}
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printf("Quad at (%2d, %2d)..(%2d, %2d) drawn"
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" for x in [%6.3f, %6.3f] and y in [%6.3f, %6.3f]\n",
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xpos, ypos,
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xpos + width, ypos + height,
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xpos + xmin, xpos + xmax,
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ypos + ymin, ypos + ymax);
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if (xmax - xmin != 1.0 - Step) {
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printf(" => Inconsistant X-axis rasterization/size!\n");
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}
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if (ymax - ymin != 1.0 - Step) {
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printf(" => Inconsistant Y-axis rasterization/size!\n");
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}
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if (xmin < -0.5) {
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printf(" => Coords should be X biased by about %f\n", 0.5 + xmin );
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}
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if (ymin < -0.5) {
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printf(" => Coords should be Y biased by about %f\n", 0.5 + ymin);
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}
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if (xmax > 0.5) {
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printf(" => Coords should be X biased by about %f\n", -xmax + 0.5);
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}
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if (ymax > 0.5) {
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printf(" => Coords should be Y biased by about %f\n", -ymax + 0.5);
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}
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}
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/**
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* Misc/disabled code for debugging.
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*/
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static void
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DebugTest(void)
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{
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glClear(GL_COLOR_BUFFER_BIT);
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glEnable(GL_BLEND);
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glBlendFunc(GL_ONE, GL_ONE);
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glColor3f(.5, .5, .5);
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glBegin(GL_LINES);
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glVertex2f(30, 35.5);
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glVertex2f(54, 35.5);
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glVertex2f(54, 35.5);
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glVertex2f(66, 35.5);
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glEnd();
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glDisable(GL_BLEND);
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glColor3f(1,1,1);
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}
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static void
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Draw(void)
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{
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glClear(GL_COLOR_BUFFER_BIT);
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glPushMatrix();
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glTranslatef(Xtrans, Ytrans, 0);
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PointCalibrate(1, 1);
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PointCalibrate(50, 50);
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PointCalibrate(28, 17);
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PointCalibrate(17, 18);
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printf("\n");
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HLineCalibrate(5, 10, 10);
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HLineCalibrate(25, 22, 12);
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HLineCalibrate(54, 33, 12);
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HLineCalibrate(54+12, 33, 12);
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printf("\n");
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QuadCalibrate(2, 2, 10, 10);
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QuadCalibrate(50, 50, 10, 10);
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QuadCalibrate(28, 17, 12, 12);
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QuadCalibrate(17, 28, 12, 12);
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(void) DebugTest;
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glPopMatrix();
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glutSwapBuffers();
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}
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static void
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Reshape(int width, int height)
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{
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Width = width;
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Height = height;
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glViewport(0, 0, width, height);
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glMatrixMode(GL_PROJECTION);
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glLoadIdentity();
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glOrtho(0, width, 0, height, -1, 1);
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glMatrixMode(GL_MODELVIEW);
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glLoadIdentity();
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}
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static void
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Key(unsigned char key, int x, int y)
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{
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(void) x;
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(void) y;
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switch (key) {
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case 27:
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glutDestroyWindow(Win);
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exit(0);
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break;
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}
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glutPostRedisplay();
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}
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static void
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Init(void)
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{
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printf("Measurement/callibration for basic prim rasterization...\n");
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printf("GL_RENDERER: %s\n", (char*) glGetString(GL_RENDERER));
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}
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int
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main(int argc, char *argv[])
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{
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glutInit(&argc, argv);
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glutInitWindowPosition(0, 0);
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glutInitWindowSize(Width, Height);
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glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
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Win = glutCreateWindow(argv[0]);
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glewInit();
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glutReshapeFunc(Reshape);
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glutKeyboardFunc(Key);
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glutDisplayFunc(Draw);
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Init();
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glutMainLoop();
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return 0;
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}
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