Add a perspective-corrected box example

.gitignore

@@ -1,3 +1,4 @@
 tri
 *.o
 .*.sw?
+box

Makefile

@@ -3,8 +3,13 @@ CBLASARGS = -L/usr/lib64/atlas -lcblas
 LINKARGS  = $(LDFLAGS) $(LD_LOAD_FLAGS) -lGL -lGLU -lGLEW -lglut $(CBLASARGS)
 VALGRIND  = valgrind --gen-suppressions=all --suppressions=support/opengl.supp --track-origins=yes --leak-check=full --show-reachable=yes
 
+all: tri box
+
 tri: Makefile tri.c utils.c
 	gcc $(CFLAGS) $(LINKARGS) tri.c -o tri
 
+box: Makefile box.c utils.c glmath.h
+	gcc $(CFLAGS) $(LINKARGS) box.c -o box
+
 %.valgrind: %
 	$(VALGRIND) ./$*

box.c

@@ -0,0 +1,202 @@
+#include <GL/glew.h>
+#include <GL/freeglut.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <jemalloc/jemalloc.h>
+#include "utils.c"
+#include "glmath.h"
+
+GLuint glprog;
+
+const char *vert_shader_file = "shaders/persp.vert";
+
+const char *frag_shader_file = "shaders/basic.frag";
+
+const float vert_data[] = {
+    0.25f,  0.25f, -1.25f, 1.0f,
+	 0.25f, -0.25f, -1.25f, 1.0f,
+	-0.25f,  0.25f, -1.25f, 1.0f,
+
+	 0.25f, -0.25f, -1.25f, 1.0f,
+	-0.25f, -0.25f, -1.25f, 1.0f,
+	-0.25f,  0.25f, -1.25f, 1.0f,
+
+	 0.25f,  0.25f, -2.75f, 1.0f,
+	-0.25f,  0.25f, -2.75f, 1.0f,
+	 0.25f, -0.25f, -2.75f, 1.0f,
+
+	 0.25f, -0.25f, -2.75f, 1.0f,
+	-0.25f,  0.25f, -2.75f, 1.0f,
+	-0.25f, -0.25f, -2.75f, 1.0f,
+
+	-0.25f,  0.25f, -1.25f, 1.0f,
+	-0.25f, -0.25f, -1.25f, 1.0f,
+	-0.25f, -0.25f, -2.75f, 1.0f,
+
+	-0.25f,  0.25f, -1.25f, 1.0f,
+	-0.25f, -0.25f, -2.75f, 1.0f,
+	-0.25f,  0.25f, -2.75f, 1.0f,
+
+	 0.25f,  0.25f, -1.25f, 1.0f,
+	 0.25f, -0.25f, -2.75f, 1.0f,
+	 0.25f, -0.25f, -1.25f, 1.0f,
+
+	 0.25f,  0.25f, -1.25f, 1.0f,
+	 0.25f,  0.25f, -2.75f, 1.0f,
+	 0.25f, -0.25f, -2.75f, 1.0f,
+
+	 0.25f,  0.25f, -2.75f, 1.0f,
+	 0.25f,  0.25f, -1.25f, 1.0f,
+	-0.25f,  0.25f, -1.25f, 1.0f,
+
+	 0.25f,  0.25f, -2.75f, 1.0f,
+	-0.25f,  0.25f, -1.25f, 1.0f,
+	-0.25f,  0.25f, -2.75f, 1.0f,
+
+	 0.25f, -0.25f, -2.75f, 1.0f,
+	-0.25f, -0.25f, -1.25f, 1.0f,
+	 0.25f, -0.25f, -1.25f, 1.0f,
+
+	 0.25f, -0.25f, -2.75f, 1.0f,
+	-0.25f, -0.25f, -2.75f, 1.0f,
+	-0.25f, -0.25f, -1.25f, 1.0f,
+
+
+
+
+	0.0f, 0.0f, 1.0f, 1.0f,
+	0.0f, 0.0f, 1.0f, 1.0f,
+	0.0f, 0.0f, 1.0f, 1.0f,
+
+	0.0f, 0.0f, 1.0f, 1.0f,
+	0.0f, 0.0f, 1.0f, 1.0f,
+	0.0f, 0.0f, 1.0f, 1.0f,
+
+	0.8f, 0.8f, 0.8f, 1.0f,
+	0.8f, 0.8f, 0.8f, 1.0f,
+	0.8f, 0.8f, 0.8f, 1.0f,
+
+	0.8f, 0.8f, 0.8f, 1.0f,
+	0.8f, 0.8f, 0.8f, 1.0f,
+	0.8f, 0.8f, 0.8f, 1.0f,
+
+	0.0f, 1.0f, 0.0f, 1.0f,
+	0.0f, 1.0f, 0.0f, 1.0f,
+	0.0f, 1.0f, 0.0f, 1.0f,
+
+	0.0f, 1.0f, 0.0f, 1.0f,
+	0.0f, 1.0f, 0.0f, 1.0f,
+	0.0f, 1.0f, 0.0f, 1.0f,
+
+	0.5f, 0.5f, 0.0f, 1.0f,
+	0.5f, 0.5f, 0.0f, 1.0f,
+	0.5f, 0.5f, 0.0f, 1.0f,
+
+	0.5f, 0.5f, 0.0f, 1.0f,
+	0.5f, 0.5f, 0.0f, 1.0f,
+	0.5f, 0.5f, 0.0f, 1.0f,
+
+	1.0f, 0.0f, 0.0f, 1.0f,
+	1.0f, 0.0f, 0.0f, 1.0f,
+	1.0f, 0.0f, 0.0f, 1.0f,
+
+	1.0f, 0.0f, 0.0f, 1.0f,
+	1.0f, 0.0f, 0.0f, 1.0f,
+	1.0f, 0.0f, 0.0f, 1.0f,
+
+	0.0f, 1.0f, 1.0f, 1.0f,
+	0.0f, 1.0f, 1.0f, 1.0f,
+	0.0f, 1.0f, 1.0f, 1.0f,
+
+	0.0f, 1.0f, 1.0f, 1.0f,
+	0.0f, 1.0f, 1.0f, 1.0f,
+	0.0f, 1.0f, 1.0f, 1.0f,
+};
+
+GLuint posbuf;
+GLuint vao;
+GLint offset_unif;
+GLint perspec_unif;
+
+void render() {
+    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+    glClear( GL_COLOR_BUFFER_BIT );
+
+    glUseProgram(glprog);
+
+    glUniform2f(offset_unif, 0.5f, 0.5f);
+
+    size_t color_index = sizeof(vert_data) / 2;
+    glBindBuffer(GL_ARRAY_BUFFER, posbuf);
+    glEnableVertexAttribArray(0);
+    glEnableVertexAttribArray(1);
+    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
+    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void *)color_index);
+
+    glDrawArrays(GL_TRIANGLES, 0, 36);
+
+    glDisableVertexAttribArray(0);
+    glDisableVertexAttribArray(1);
+    glUseProgram(0);
+
+    glutSwapBuffers();
+    glutPostRedisplay();
+}
+
+void resize(int w, int h) {
+    h = h ? h : 1;
+    glViewport(0, 0, w, h);
+}
+
+void init() {
+    GLuint shaders[2];
+    shaders[0] = load_shader(GL_VERTEX_SHADER, vert_shader_file);
+    shaders[1] = load_shader(GL_FRAGMENT_SHADER, frag_shader_file);
+
+    glprog = create_program(2, shaders);
+    offset_unif = glGetUniformLocation(glprog, "offset");
+    perspec_unif = glGetUniformLocation(glprog, "perspective");
+    mat44f perspec;
+    perspective_matrix(1.0f, 0.5f, 3.0f, perspec);
+    for (int i = 0; i<16; i++) {
+        printf("%2f\n", ((float *)perspec)[i]);
+    }
+
+    glUseProgram(glprog);
+    glUniformMatrix4fv(perspec_unif, 1, GL_TRUE, (GLfloat *)perspec);
+    glUseProgram(0);
+
+    glGenBuffers(1, &posbuf);
+    glBindBuffer(GL_ARRAY_BUFFER, posbuf);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vert_data), vert_data, GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+
+    glEnable(GL_CULL_FACE);
+    glCullFace(GL_BACK);
+    glFrontFace(GL_CW);
+}
+
+int main(int argc, char **argv) {
+    glutInit(&argc, argv);
+    glutInitDisplayMode( GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGB );
+
+    glutCreateWindow("tritest");
+    glutDisplayFunc(render);
+    //glutIdleFunc(render);
+    glutReshapeFunc(resize);
+
+    glewInit();
+    if (!glewIsSupported("GL_VERSION_2_0")) {
+        printf("OpenGL 2.0 not supported\n");
+        exit(1);
+    }
+
+    init();
+
+    glutMainLoop();
+
+    return 0;
+}

glmath.h

@@ -1,5 +1,16 @@
+#include <string.h>
+#include <GL/glew.h>
 #include <cblas.h>
-typedef double vec4d[4];
-typedef double mat44d[4][4];
+typedef GLfloat vec4f[4];
+typedef GLfloat mat44f[4][4];
 
-#define mvmul4d(m,v,r) cblas_dgemv(CblasRowMajor, CblasNoTrans, 4, 4, 1.0, (double *)m, 4, (double *)v, 1, 0.0, r, 1);
+#define mvmul4f(m,v,r) cblas_dgemv(CblasRowMajor, CblasNoTrans, 4, 4, 1.0, (float *)m, 4, (float *)v, 1, 0.0, r, 1);
+
+void perspective_matrix(float scale, float znear, float zfar, mat44f p) {
+    memset(p, 0, 16 * sizeof(float));
+    p[0][0] = scale;
+    p[1][1] = scale;
+    p[2][2] = (znear+zfar)/(znear-zfar);
+    p[3][2] = (2*znear*zfar)/(znear-zfar);
+    p[2][3] = -1.0f;
+}

shaders/persp.vert

@@ -0,0 +1,13 @@
+#version 330
+layout(location = 0) in vec4 position;
+layout(location = 1) in vec4 color;
+smooth out vec4 gl_Color;
+
+uniform vec2 offset;
+uniform mat4 perspective;
+void main()
+{
+    vec4 cp = position + vec4(offset.x, offset.y, 0.0, 0.0);
+    gl_Position = perspective * cp;
+    gl_Color = color;
+}