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