| /** |
| * Test two-sided lighting with shaders. |
| * Both GL_VERTEX_PROGRAM_TWO_SIDE and gl_FrontFacing can be tested |
| * (see keys below). |
| * |
| * Brian Paul |
| * 18 Dec 2007 |
| */ |
| |
| #include <assert.h> |
| #include <string.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <math.h> |
| #include <GL/glew.h> |
| #include <GL/glut.h> |
| #include "shaderutil.h" |
| |
| #ifndef M_PI |
| #define M_PI 3.1415926535 |
| #endif |
| |
| 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; |
| static GLboolean DetermineFacingInFragProg; |
| static GLfloat Xrot; |
| static GLint u_fragface; |
| static GLenum FrontWinding; |
| static int prevTime = 0; |
| |
| |
| static const GLfloat Red[4] = {1, 0, 0, 1}; |
| static const GLfloat Green[4] = {0, 1, 0, 0}; |
| |
| |
| static void |
| SetDefaults(void) |
| { |
| DetermineFacingInFragProg = GL_TRUE; |
| FrontWinding = GL_CCW; |
| Xrot = 30; |
| anim = 0; |
| glutIdleFunc(NULL); |
| } |
| |
| |
| static void |
| Redisplay(void) |
| { |
| const int sections = 20; |
| int i; |
| float radius = 2; |
| |
| glFrontFace(FrontWinding); |
| |
| if (DetermineFacingInFragProg) { |
| glUniform1i(u_fragface, 1); |
| glDisable(GL_VERTEX_PROGRAM_TWO_SIDE); |
| } |
| else { |
| glUniform1i(u_fragface, 0); |
| glEnable(GL_VERTEX_PROGRAM_TWO_SIDE); |
| } |
| |
| glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); |
| |
| glPushMatrix(); |
| glRotatef(Xrot, 1, 0, 0); |
| |
| /* Draw a tristrip ring */ |
| glBegin(GL_TRIANGLE_STRIP); |
| glColor4fv(Red); |
| glSecondaryColor3fv(Green); |
| for (i = 0; i <= sections; i++) { |
| float a = (float) i / (sections) * M_PI * 2.0; |
| float x = radius * cos(a); |
| float y = radius * sin(a); |
| glVertex3f(x, -1, y); |
| glVertex3f(x, +1, y); |
| } |
| glEnd(); |
| |
| glPopMatrix(); |
| |
| glutSwapBuffers(); |
| } |
| |
| |
| static void |
| Idle(void) |
| { |
| int curTime = glutGet(GLUT_ELAPSED_TIME); |
| int dt = curTime - prevTime; |
| |
| if (prevTime == 0) { |
| prevTime = curTime; |
| return; |
| } |
| prevTime = curTime; |
| |
| Xrot += dt * 0.1; |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| Reshape(int width, int height) |
| { |
| float ar = (float) width / height; |
| glViewport(0, 0, width, height); |
| glMatrixMode(GL_PROJECTION); |
| glLoadIdentity(); |
| glFrustum(-ar, ar, -1, 1, 3, 25); |
| glMatrixMode(GL_MODELVIEW); |
| glLoadIdentity(); |
| glTranslatef(0, 0, -10); |
| } |
| |
| |
| static void |
| CleanUp(void) |
| { |
| glDeleteShader(fragShader); |
| glDeleteShader(vertShader); |
| glDeleteProgram(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) { |
| prevTime = glutGet(GLUT_ELAPSED_TIME); |
| glutIdleFunc(Idle); |
| } |
| else |
| glutIdleFunc(NULL); |
| break; |
| case 'f': |
| printf("Using frag shader gl_FrontFacing\n"); |
| DetermineFacingInFragProg = GL_TRUE; |
| break; |
| case 'v': |
| printf("Using vert shader Two-sided lighting\n"); |
| DetermineFacingInFragProg = GL_FALSE; |
| break; |
| case 'r': |
| /* reset */ |
| SetDefaults(); |
| break; |
| case 's': |
| Xrot += 5; |
| break; |
| case 'S': |
| Xrot -= 5; |
| break; |
| case 'w': |
| if (FrontWinding == GL_CCW) { |
| FrontWinding = GL_CW; |
| printf("FrontFace = GL_CW\n"); |
| } |
| else { |
| FrontWinding = GL_CCW; |
| printf("FrontFace = GL_CCW\n"); |
| } |
| break; |
| case 27: |
| CleanUp(); |
| exit(0); |
| break; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| Init(void) |
| { |
| static const char *fragShaderText = |
| "uniform bool fragface; \n" |
| "void main() { \n" |
| #if 1 |
| " if (!fragface || gl_FrontFacing) { \n" |
| " gl_FragColor = gl_Color; \n" |
| " } \n" |
| " else { \n" |
| " // note: dim green to help debug \n" |
| " gl_FragColor = 0.8 * gl_SecondaryColor; \n" |
| " } \n" |
| #else |
| /* DEBUG CODE */ |
| " bool f = gl_FrontFacing; \n" |
| " if (f) { \n" |
| " gl_FragColor = vec4(1.0, 0.0, 0.0, 0.0); \n" |
| " } \n" |
| " else { \n" |
| " gl_FragColor = vec4(0.0, 1.0, 0.0, 0.0); \n" |
| " } \n" |
| #endif |
| "} \n"; |
| static const char *vertShaderText = |
| "uniform bool fragface; \n" |
| "void main() { \n" |
| " gl_FrontColor = gl_Color; \n" |
| " if (fragface) { \n" |
| " // front/back chosen in frag prog \n" |
| " gl_FrontSecondaryColor = gl_SecondaryColor; \n" |
| " } \n" |
| " else { \n" |
| " // front/back chosen in prim setup \n" |
| " gl_BackColor = gl_SecondaryColor; \n" |
| " } \n" |
| " gl_Position = ftransform(); \n" |
| "} \n"; |
| |
| if (!ShadersSupported()) |
| exit(1); |
| |
| vertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText); |
| fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText); |
| program = LinkShaders(vertShader, fragShader); |
| |
| glUseProgram(program); |
| |
| u_fragface = glGetUniformLocation(program, "fragface"); |
| printf("Uniforms: %d\n", u_fragface); |
| |
| /*assert(glGetError() == 0);*/ |
| |
| glClearColor(0.3f, 0.3f, 0.3f, 0.0f); |
| |
| printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER)); |
| |
| assert(glIsProgram(program)); |
| assert(glIsShader(fragShader)); |
| assert(glIsShader(vertShader)); |
| |
| glEnable(GL_DEPTH_TEST); |
| |
| SetDefaults(); |
| } |
| |
| |
| 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]; |
| } |
| } |
| } |
| |
| |
| static void |
| Usage(void) |
| { |
| printf("Keys:\n"); |
| printf(" f - do front/back determination in fragment shader\n"); |
| printf(" v - do front/back determination in vertex shader\n"); |
| printf(" r - reset, show front\n"); |
| printf(" a - toggle animation\n"); |
| printf(" s - step rotation\n"); |
| printf(" w - toggle CW, CCW front-face winding\n"); |
| printf("NOTE: red = front face, green = back face.\n"); |
| } |
| |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| glutInit(&argc, argv); |
| glutInitWindowSize(WinWidth, WinHeight); |
| glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE); |
| win = glutCreateWindow(argv[0]); |
| glewInit(); |
| glutReshapeFunc(Reshape); |
| glutKeyboardFunc(Key); |
| glutDisplayFunc(Redisplay); |
| if (anim) |
| glutIdleFunc(Idle); |
| ParseOptions(argc, argv); |
| Init(); |
| Usage(); |
| glutMainLoop(); |
| return 0; |
| } |