--- /dev/null
+/**
+ * Demonstration of doing triangle rasterization with a fragment program.
+ * Basic idea:
+ * 1. Draw screen-aligned quad / bounding box around the triangle verts.
+ * 2. For each pixel in the quad, determine if pixel is inside/outside
+ * the triangle edges.
+ *
+ * Brian Paul
+ * 1 Aug 2007
+ */
+
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/gl.h>
+#include <GL/glut.h>
+#include <GL/glext.h>
+#include "extfuncs.h"
+
+
+static GLint WinWidth = 300, WinHeight = 300;
+static char *FragProgFile = NULL;
+static char *VertProgFile = NULL;
+static GLuint fragShader;
+static GLuint vertShader;
+static GLuint program;
+static GLint win = 0;
+static GLboolean anim = GL_TRUE;
+static GLfloat Zrot = 0.0f;
+static GLint uv0, uv1, uv2;
+
+
+static const GLfloat TriVerts[3][2] = {
+ { 50, 50 },
+ { 250, 50 },
+ { 150, 250 }
+};
+
+
+static void
+RotateVerts(GLfloat a,
+ GLuint n, const GLfloat vertsIn[][2], GLfloat vertsOut[][2])
+{
+ GLuint i;
+ GLfloat cx = WinWidth / 2, cy = WinHeight / 2;
+ for (i = 0; i < n; i++) {
+ float x = vertsIn[i][0] - cx;
+ float y = vertsIn[i][1] - cy;
+
+ vertsOut[i][0] = x * cos(a) + y * sin(a) + cx;
+ vertsOut[i][1] = -x * sin(a) + y * cos(a) + cy;
+ }
+}
+
+static void
+ComputeBounds(GLuint n, GLfloat vertsIn[][2],
+ GLfloat *xmin, GLfloat *ymin,
+ GLfloat *xmax, GLfloat *ymax)
+{
+ GLuint i;
+ *xmin = *xmax = vertsIn[0][0];
+ *ymin = *ymax = vertsIn[0][1];
+ for (i = 1; i < n; i++) {
+ if (vertsIn[i][0] < *xmin)
+ *xmin = vertsIn[i][0];
+ else if (vertsIn[i][0] > *xmax)
+ *xmax = vertsIn[i][0];
+ if (vertsIn[i][1] < *ymin)
+ *ymin = vertsIn[i][1];
+ else if (vertsIn[i][1] > *ymax)
+ *ymax = vertsIn[i][1];
+ }
+}
+
+
+static void
+Redisplay(void)
+{
+ GLfloat v[3][2], xmin, ymin, xmax, ymax;
+
+ RotateVerts(Zrot, 3, TriVerts, v);
+ ComputeBounds(3, v, &xmin, &ymin, &xmax, &ymax);
+
+ glUniform2fv_func(uv0, 1, v[0]);
+ glUniform2fv_func(uv1, 1, v[1]);
+ glUniform2fv_func(uv2, 1, v[2]);
+
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+ glPushMatrix();
+ glBegin(GL_POLYGON);
+ glVertex2f(xmin, ymin);
+ glVertex2f(xmax, ymin);
+ glVertex2f(xmax, ymax);
+ glVertex2f(xmin, ymax);
+ glEnd();
+ glPopMatrix();
+
+ glutSwapBuffers();
+}
+
+
+static void
+Idle(void)
+{
+ Zrot = glutGet(GLUT_ELAPSED_TIME) * 0.0005;
+ glutPostRedisplay();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+ glViewport(0, 0, width, height);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ glOrtho(0, width, 0, height, -1, 1);
+
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+}
+
+
+static void
+CleanUp(void)
+{
+ glDeleteShader_func(fragShader);
+ glDeleteShader_func(vertShader);
+ glDeleteProgram_func(program);
+ glutDestroyWindow(win);
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+ (void) x;
+ (void) y;
+
+ switch(key) {
+ case ' ':
+ case 'a':
+ anim = !anim;
+ if (anim)
+ glutIdleFunc(Idle);
+ else
+ glutIdleFunc(NULL);
+ break;
+ case 27:
+ CleanUp();
+ exit(0);
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void
+LoadAndCompileShader(GLuint shader, const char *text)
+{
+ GLint stat;
+
+ glShaderSource_func(shader, 1, (const GLchar **) &text, NULL);
+
+ glCompileShader_func(shader);
+
+ glGetShaderiv_func(shader, GL_COMPILE_STATUS, &stat);
+ if (!stat) {
+ GLchar log[1000];
+ GLsizei len;
+ glGetShaderInfoLog_func(shader, 1000, &len, log);
+ fprintf(stderr, "fslight: problem compiling shader:\n%s\n", log);
+ exit(1);
+ }
+}
+
+
+/**
+ * Read a shader from a file.
+ */
+static void
+ReadShader(GLuint shader, const char *filename)
+{
+ const int max = 100*1000;
+ int n;
+ char *buffer = (char*) malloc(max);
+ FILE *f = fopen(filename, "r");
+ if (!f) {
+ fprintf(stderr, "fslight: Unable to open shader file %s\n", filename);
+ exit(1);
+ }
+
+ n = fread(buffer, 1, max, f);
+ printf("fslight: read %d bytes from shader file %s\n", n, filename);
+ if (n > 0) {
+ buffer[n] = 0;
+ LoadAndCompileShader(shader, buffer);
+ }
+
+ fclose(f);
+ free(buffer);
+}
+
+
+static void
+CheckLink(GLuint prog)
+{
+ GLint stat;
+ glGetProgramiv_func(prog, GL_LINK_STATUS, &stat);
+ if (!stat) {
+ GLchar log[1000];
+ GLsizei len;
+ glGetProgramInfoLog_func(prog, 1000, &len, log);
+ fprintf(stderr, "Linker error:\n%s\n", log);
+ }
+}
+
+
+static void
+Init(void)
+{
+ static const char *fragShaderText =
+ "uniform vec2 v0, v1, v2; \n"
+ "float crs(const vec2 u, const vec2 v) \n"
+ "{ \n"
+ " return u.x * v.y - u.y * v.x; \n"
+ "} \n"
+ "\n"
+ "void main() {\n"
+ " vec2 p = gl_FragCoord.xy; \n"
+ " if (crs(v1 - v0, p - v0) >= 0 && \n"
+ " crs(v2 - v1, p - v1) >= 0 && \n"
+ " crs(v0 - v2, p - v2) >= 0) \n"
+ " gl_FragColor = vec4(1.0); \n"
+ " else \n"
+ " gl_FragColor = vec4(0.5); \n"
+ "}\n";
+ static const char *vertShaderText =
+ "void main() {\n"
+ " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+ "}\n";
+ const char *version;
+
+ version = (const char *) glGetString(GL_VERSION);
+ if (version[0] != '2' || version[1] != '.') {
+ printf("This program requires OpenGL 2.x, found %s\n", version);
+ exit(1);
+ }
+
+ GetExtensionFuncs();
+
+ fragShader = glCreateShader_func(GL_FRAGMENT_SHADER);
+ if (FragProgFile)
+ ReadShader(fragShader, FragProgFile);
+ else
+ LoadAndCompileShader(fragShader, fragShaderText);
+
+ vertShader = glCreateShader_func(GL_VERTEX_SHADER);
+ if (VertProgFile)
+ ReadShader(vertShader, VertProgFile);
+ else
+ LoadAndCompileShader(vertShader, vertShaderText);
+
+ program = glCreateProgram_func();
+ glAttachShader_func(program, fragShader);
+ glAttachShader_func(program, vertShader);
+ glLinkProgram_func(program);
+ CheckLink(program);
+ glUseProgram_func(program);
+
+ uv0 = glGetUniformLocation_func(program, "v0");
+ uv1 = glGetUniformLocation_func(program, "v1");
+ uv2 = glGetUniformLocation_func(program, "v2");
+ printf("Uniforms: %d %d %d\n", uv0, uv1, uv2);
+
+ /*assert(glGetError() == 0);*/
+
+ glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
+ glEnable(GL_DEPTH_TEST);
+
+ printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
+
+ assert(glIsProgram_func(program));
+ assert(glIsShader_func(fragShader));
+ assert(glIsShader_func(vertShader));
+
+ glColor3f(1, 0, 0);
+}
+
+
+static void
+ParseOptions(int argc, char *argv[])
+{
+ int i;
+ for (i = 1; i < argc; i++) {
+ if (strcmp(argv[i], "-fs") == 0) {
+ FragProgFile = argv[i+1];
+ }
+ else if (strcmp(argv[i], "-vs") == 0) {
+ VertProgFile = argv[i+1];
+ }
+ }
+}
+
+
+int
+main(int argc, char *argv[])
+{
+ glutInit(&argc, argv);
+ glutInitWindowPosition( 0, 0);
+ glutInitWindowSize(WinWidth, WinHeight);
+ glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
+ win = glutCreateWindow(argv[0]);
+ glutReshapeFunc(Reshape);
+ glutKeyboardFunc(Key);
+ glutDisplayFunc(Redisplay);
+ if (anim)
+ glutIdleFunc(Idle);
+ ParseOptions(argc, argv);
+ Init();
+ glutMainLoop();
+ return 0;
+}
projects / mesa.git / commitdiff