Attachment 117029 Details for Bug 91292 – Complete small program to demonstrate problem. Compile instructions in source

Complete small program to demonstrate problem. Compile instructions in source

divAttrib.c (text/plain), 5.07 KB, created by Hugh Fisher on 2015-07-10 13:39:00 UTC

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Creator: Hugh Fisher

Created: 2015-07-10 13:39:00 UTC

Size: 5.07 KB

patch

obsolete

>
>
>/*
>    Hugh Fisher Jul 2015
>    Demo use of attribute divisor for instancing
>
>    gcc divAttrib.c -o divAttrib -lGL -lglut
>
>    Expected output: blue window with triangles
>    arranged around a square, not quite centred
>    
>
>*/
>
>#include <stdio.h>
>
>#include <GL/gl.h>
>#include <GL/freeglut_std.h>
>#include <GL/freeglut_ext.h>
>
>void Fail(const char * format, ...)
>{
>    va_list ap;
>
>    va_start(ap, format);
>    vfprintf(stderr, format, ap);
>    va_end(ap);
>
>    exit(-1);
>}
>
>void CheckGL(const char * where)
>{
>    GLenum  err;
>    const char *  msg;
>
>    err = glGetError();
>    if (err != GL_NO_ERROR) {
>        // no gluGetErrorString in GL3/4. Ridiculous
>        if (err == GL_INVALID_ENUM)
>            msg = "Invalid enum";
>        else if (err == GL_INVALID_VALUE)
>            msg = "Invalid value";
>        else if (err == GL_INVALID_OPERATION)
>            msg = "Invalid operation";
>        else if (err == GL_OUT_OF_MEMORY)
>            msg = "Out of memory";
>        else if (err == GL_INVALID_FRAMEBUFFER_OPERATION)
>            msg = "Invalid frame buffer operation";
>         else
>            msg = "";
>        Fail("%s OpenGL error: %d %s", where, err, msg);
>    }
>}
>
>/*  Shaders. */
>
>static const char * vertShaderCode = "\
>#version 330\n\
>in vec4 vVertex;\n\
>in vec2 vOffset;\n\
>out vec4 vVaryingColor;\n\
>void main ()\n\
>{\n\
>    gl_Position = vVertex + vec4(vOffset.x, vOffset.y, 0, 0);\n\
>    vVaryingColor = vec4(1, 0, 0, 1);\n\
>}\n\
>";
>
>static const char * fragShaderCode = "\
>#version 330\n\
>in  vec4 vVaryingColor;\n\
>out vec4 vFragColor;\n\
>void main ()\n\
>{\n\
>    vFragColor = vVaryingColor;\n\
>}\n\
>";
>
>static GLint    prog;
>
>static GLint buildShader(GLint kind, const char * source)
>{
>    GLuint      shader;
>    const GLchar * src[1];
>    GLint       ok;
>    char        buf[512];
>    GLsizei     len;
>
>    shader = glCreateShader(kind);
>    src[0] = source;
>    glShaderSource(shader, 1, src, NULL);
>
>    /* Now compile and report any errors */
>    glCompileShader(shader);
>    glGetShaderiv(shader, GL_COMPILE_STATUS, &ok);
>    if (! ok) {
>        glGetShaderInfoLog(shader, sizeof(buf), &len, (GLchar *)buf);
>        buf[len] = 0;
>        Fail("Error in shader kind %d: %s", kind, buf);
>    }
>    return shader;
>
>}
>static void initProgram()
>{
>    GLint   vert, frag;
>    GLint   ok;
>    char    buf[512];
>    GLsizei len;
>    const GLchar * src[1];
>
>    prog = glCreateProgram();
>    glBindAttribLocation(prog, 0, "vVertex");
>    glBindAttribLocation(prog, 1, "vOffset");
>
>    vert = buildShader(GL_VERTEX_SHADER, vertShaderCode);
>    frag = buildShader(GL_FRAGMENT_SHADER, fragShaderCode);
>
>    glAttachShader(prog, vert);
>    glAttachShader(prog, frag);
>    glLinkProgram(prog);
>    glGetProgramiv(prog, GL_LINK_STATUS, &ok);
>    if (! ok) {
>        glGetProgramInfoLog(prog, sizeof(buf), &len, (GLchar *)buf);
>        buf[len] = 0;
>        Fail("Error linking GPU program: %s", buf);
>    }
>
>    glEnable(GL_PROGRAM_POINT_SIZE);
>    
>    CheckGL("initProgram");
>}
>
>/*  Just drawing one triangle */
>
>static GLint    vboA;
>static GLint    vBuf;
>static GLint	oBuf;
>
>#define NVERTS  3
>static GLfloat vertData[NVERTS * 4] = {
>    -0.25, 0, 0, 1,
>     0.25, 0, 0, 1,
>     0, 0.433, 0, 1,
>};
>
>/* But 8 copies, offset around origin */
>
>#define NTRIS 8
>static GLfloat offsetData[NTRIS * 2] = {
>    -0.5, -0.5,
>     0,   -0.5,
>     0.5, -0.5,
>    -0.5,  0,
>     0.5,  0,
>    -0.5,  0.5,
>     0,    0.5,
>     0.5,  0.5,
>};
>
>static void initGeo()
>{
>    glGenVertexArrays(1, &vboA);
>    glBindVertexArray(vboA);
>
>    // Single attribute, vertex position
>    glGenBuffers(1, &vBuf);
>    glBindBuffer(GL_ARRAY_BUFFER, vBuf);
>    glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 4 * NVERTS, vertData, GL_STATIC_DRAW);
>    glEnableVertexAttribArray(0);
>    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
>    // Per-triangle attribute, offset
>    glGenBuffers(1, &oBuf);
>    glBindBuffer(GL_ARRAY_BUFFER, oBuf);
>    glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 2 * NTRIS, offsetData, GL_STATIC_DRAW);
>    glEnableVertexAttribArray(1);
>    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, 0);
>    glVertexAttribDivisor(1, 1);
>
>    // Done
>    glBindVertexArray(0);
>    glBindBuffer(GL_ARRAY_BUFFER, 0);
>    CheckGL("initGeo");
>}
>
>/*  Main program    */
>
>void ChangeSize(int w, int h)
>{
>    printf("Resize %d x %d\n", w, h);
>    glViewport(0, 0, w, h);
>}
>
>void DrawWindow()
>{
>    printf("Draw!\n");
>    glClearColor(0, 0, 1, 0);
>    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
>
>    glBindVertexArray(vboA);
>    glUseProgram(prog);
>    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
>    glLineWidth(2);
>    glDrawArraysInstanced(GL_TRIANGLES, 0, 3, NTRIS);
>
>    glutSwapBuffers();
>    CheckGL("DrawWindow");
>}
>
>
>int main(int argc, char* argv[])
>{
>    glutInit(&argc, argv);
>    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
>    glutInitWindowSize(256, 256);
>    glutInitContextVersion(3,3);
>    glutInitContextProfile(GLUT_CORE_PROFILE);
>    glutCreateWindow("Attribute divisor demo");
>
>    glEnable(GL_DEPTH_TEST);
>    initGeo();
>    initProgram();
>    
>    glutReshapeFunc(ChangeSize);
>    glutDisplayFunc(DrawWindow);
>
>    glutMainLoop();
>}

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Attachments on bug 91292: 117029 | 117030 | 117049

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