| /** |
| * Test variable array indexing in a vertex shader. |
| * Brian Paul |
| * 17 April 2009 |
| */ |
| |
| #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" |
| |
| |
| /** |
| * The vertex position.z is used as a (variable) index into an |
| * array which returns a new Z value. |
| */ |
| static const char *VertShaderText = |
| "uniform sampler2D tex1; \n" |
| "uniform float HeightArray[20]; \n" |
| "void main() \n" |
| "{ \n" |
| " vec4 pos = gl_Vertex; \n" |
| " int i = int(pos.z * 9.5); \n" |
| " pos.z = HeightArray[i]; \n" |
| " gl_Position = gl_ModelViewProjectionMatrix * pos; \n" |
| " gl_FrontColor = pos; \n" |
| "} \n"; |
| |
| static const char *FragShaderText = |
| "void main() \n" |
| "{ \n" |
| " gl_FragColor = gl_Color; \n" |
| "} \n"; |
| |
| |
| static GLuint fragShader; |
| static GLuint vertShader; |
| static GLuint program; |
| |
| static GLint win = 0; |
| static GLboolean Anim = GL_TRUE; |
| static GLboolean WireFrame = GL_TRUE; |
| static GLfloat xRot = -70.0f, yRot = 0.0f, zRot = 0.0f; |
| |
| |
| static void |
| Idle(void) |
| { |
| zRot = 90 + glutGet(GLUT_ELAPSED_TIME) * 0.05; |
| glutPostRedisplay(); |
| } |
| |
| |
| /** z=f(x,y) */ |
| static float |
| fz(float x, float y) |
| { |
| return fabs(cos(1.5*x) + cos(1.5*y)); |
| } |
| |
| |
| static void |
| DrawMesh(void) |
| { |
| GLfloat xmin = -2.0, xmax = 2.0; |
| GLfloat ymin = -2.0, ymax = 2.0; |
| GLuint xdivs = 20, ydivs = 20; |
| GLfloat dx = (xmax - xmin) / xdivs; |
| GLfloat dy = (ymax - ymin) / ydivs; |
| GLfloat ds = 1.0 / xdivs, dt = 1.0 / ydivs; |
| GLfloat x, y, s, t; |
| GLuint i, j; |
| |
| y = ymin; |
| t = 0.0; |
| for (i = 0; i < ydivs; i++) { |
| x = xmin; |
| s = 0.0; |
| glBegin(GL_QUAD_STRIP); |
| for (j = 0; j < xdivs; j++) { |
| float z0 = fz(x, y), z1 = fz(x, y + dy); |
| |
| glTexCoord2f(s, t); |
| glVertex3f(x, y, z0); |
| |
| glTexCoord2f(s, t + dt); |
| glVertex3f(x, y + dy, z1); |
| x += dx; |
| s += ds; |
| } |
| glEnd(); |
| y += dy; |
| t += dt; |
| } |
| } |
| |
| |
| static void |
| Redisplay(void) |
| { |
| glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); |
| |
| if (WireFrame) |
| glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); |
| else |
| glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); |
| |
| glPushMatrix(); |
| glRotatef(xRot, 1.0f, 0.0f, 0.0f); |
| glRotatef(yRot, 0.0f, 1.0f, 0.0f); |
| glRotatef(zRot, 0.0f, 0.0f, 1.0f); |
| |
| glPushMatrix(); |
| DrawMesh(); |
| glPopMatrix(); |
| |
| glPopMatrix(); |
| |
| glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); |
| |
| glutSwapBuffers(); |
| } |
| |
| |
| static void |
| Reshape(int width, int height) |
| { |
| glViewport(0, 0, width, height); |
| glMatrixMode(GL_PROJECTION); |
| glLoadIdentity(); |
| glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0); |
| glMatrixMode(GL_MODELVIEW); |
| glLoadIdentity(); |
| glTranslatef(0.0f, 0.0f, -15.0f); |
| } |
| |
| |
| static void |
| CleanUp(void) |
| { |
| glDeleteShader(fragShader); |
| glDeleteShader(vertShader); |
| glDeleteProgram(program); |
| glutDestroyWindow(win); |
| } |
| |
| |
| static void |
| Key(unsigned char key, int x, int y) |
| { |
| const GLfloat step = 2.0; |
| (void) x; |
| (void) y; |
| |
| switch(key) { |
| case 'a': |
| Anim = !Anim; |
| if (Anim) |
| glutIdleFunc(Idle); |
| else |
| glutIdleFunc(NULL); |
| break; |
| case 'w': |
| WireFrame = !WireFrame; |
| break; |
| case 'z': |
| zRot += step; |
| break; |
| case 'Z': |
| zRot -= step; |
| break; |
| case 27: |
| CleanUp(); |
| exit(0); |
| break; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| SpecialKey(int key, int x, int y) |
| { |
| const GLfloat step = 2.0; |
| |
| (void) x; |
| (void) y; |
| |
| switch(key) { |
| case GLUT_KEY_UP: |
| xRot += step; |
| break; |
| case GLUT_KEY_DOWN: |
| xRot -= step; |
| break; |
| case GLUT_KEY_LEFT: |
| yRot -= step; |
| break; |
| case GLUT_KEY_RIGHT: |
| yRot += step; |
| break; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| Init(void) |
| { |
| GLfloat HeightArray[20]; |
| GLint u, i; |
| |
| if (!ShadersSupported()) |
| exit(1); |
| |
| vertShader = CompileShaderText(GL_VERTEX_SHADER, VertShaderText); |
| fragShader = CompileShaderText(GL_FRAGMENT_SHADER, FragShaderText); |
| program = LinkShaders(vertShader, fragShader); |
| |
| glUseProgram(program); |
| |
| /* Setup the HeightArray[] uniform */ |
| for (i = 0; i < 20; i++) |
| HeightArray[i] = i / 20.0; |
| u = glGetUniformLocation(program, "HeightArray"); |
| glUniform1fv(u, 20, HeightArray); |
| |
| assert(glGetError() == 0); |
| |
| glClearColor(0.4f, 0.4f, 0.8f, 0.0f); |
| glEnable(GL_DEPTH_TEST); |
| glColor3f(1, 1, 1); |
| } |
| |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| glutInit(&argc, argv); |
| glutInitWindowSize(500, 500); |
| glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH); |
| win = glutCreateWindow(argv[0]); |
| glewInit(); |
| glutReshapeFunc(Reshape); |
| glutKeyboardFunc(Key); |
| glutSpecialFunc(SpecialKey); |
| glutDisplayFunc(Redisplay); |
| Init(); |
| if (Anim) |
| glutIdleFunc(Idle); |
| glutMainLoop(); |
| return 0; |
| } |
| |