Test the GL_ARB_draw_buffers extension.

Also requires GL_EXT_framebuffer_object and OpenGL 2.0 (for GLSL).

diff --git a/progs/tests/drawbuffers.c b/progs/tests/drawbuffers.c
new file mode 100644 (file)
index 0000000..8583bac
--- /dev/null
+++ b/progs/tests/drawbuffers.c
@@ -0,0 +1,298 @@
+/*
+ * Test GL_ARB_draw_buffers, GL_EXT_framebuffer_object
+ * and GLSL's gl_FragData[].
+ *
+ * Brian Paul
+ * 11 March 2007
+ */
+
+
+#define GL_GLEXT_PROTOTYPES
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/glut.h>
+#include "extfuncs.h"
+
+static int Win;
+static int Width = 400, Height = 400;
+static GLuint FBobject, RBobjects[3];
+static GLfloat Xrot = 0.0, Yrot = 0.0;
+
+
+static void
+CheckError(int line)
+{
+   GLenum err = glGetError();
+   if (err) {
+      printf("GL Error 0x%x at line %d\n", (int) err, line);
+   }
+}
+
+
+static void
+Display(void)
+{
+   GLubyte *buffer = malloc(Width * Height * 4);
+   static const GLenum buffers[2] = {
+      GL_COLOR_ATTACHMENT0_EXT,
+      GL_COLOR_ATTACHMENT1_EXT
+   };
+
+   /* draw to user framebuffer */
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBobject);
+
+   /* Clear color buffer 0 (blue) */
+   glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
+   glClearColor(0.5, 0.5, 1.0, 0.0);
+   glClear(GL_COLOR_BUFFER_BIT);
+
+   /* Clear color buffer 1 (1 - blue) */
+   glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
+   glClearColor(0.5, 0.5, 0.0, 0.0);
+   glClear(GL_COLOR_BUFFER_BIT);
+
+   glClear(GL_DEPTH_BUFFER_BIT);
+
+   /* draw to two buffers w/ fragment shader */
+   glDrawBuffersARB(2, buffers);
+
+   glPushMatrix();
+   glRotatef(Xrot, 1, 0, 0);
+   glRotatef(Yrot, 0, 1, 0);
+   glutSolidTorus(0.75, 2.0, 10, 20);
+   glPopMatrix();
+
+   /* read from user framebuffer */
+   /* bottom half = colorbuffer 0 */
+   glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
+   glReadPixels(0, 0, Width, Height / 2, GL_RGBA, GL_UNSIGNED_BYTE,
+                buffer);
+   /* top half = colorbuffer 1 */
+   glReadBuffer(GL_COLOR_ATTACHMENT1_EXT);
+   glReadPixels(0, Height/2, Width, Height / 2, GL_RGBA, GL_UNSIGNED_BYTE,
+                buffer + Width * Height / 2 * 4);
+
+   /* draw to window */
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+   glWindowPos2iARB(0, 0);
+   glDrawPixels(Width, Height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
+
+   free(buffer);
+   glutSwapBuffers();
+   CheckError(__LINE__);
+}
+
+
+static void
+Reshape(int width, int height)
+{
+   float ar = (float) width / (float) height;
+
+   glViewport(0, 0, width, height);
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glFrustum(-ar, ar, -1.0, 1.0, 5.0, 35.0);
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+   glTranslatef(0.0, 0.0, -20.0);
+
+   Width = width;
+   Height = height;
+
+   glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[0]);
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
+   glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[1]);
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
+   glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[2]);
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT,
+                            Width, Height);
+}
+
+
+static void
+CleanUp(void)
+{
+   glDeleteFramebuffersEXT(1, &FBobject);
+   glDeleteRenderbuffersEXT(3, RBobjects);
+   glutDestroyWindow(Win);
+   exit(0);
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+      case 'x':
+         Xrot += 5.0;
+         break;
+      case 'y':
+         Yrot += 5.0;
+         break;
+      case 27:
+         CleanUp();
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+CheckExtensions(void)
+{
+   const char *version = (const char *) glGetString(GL_VERSION);
+   GLint numBuf;
+
+   if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
+      printf("Sorry, GL_EXT_framebuffer_object is required!\n");
+      exit(1);
+   }
+   if (!glutExtensionSupported("GL_ARB_draw_buffers")) {
+      printf("Sorry, GL_ARB_draw_buffers is required!\n");
+      exit(1);
+   }
+   if (version[0] != '2') {
+      printf("Sorry, OpenGL 2.0 is required!\n");
+      exit(1);
+   }
+
+   glGetIntegerv(GL_MAX_DRAW_BUFFERS_ARB, &numBuf);
+   printf("GL_MAX_DRAW_BUFFERS_ARB = %d\n", numBuf);
+   if (numBuf < 2) {
+      printf("Sorry, GL_MAX_DRAW_BUFFERS_ARB needs to be >= 2\n");
+      exit(1);
+   }
+
+   printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
+}
+
+
+static void
+SetupRenderbuffers(void)
+{
+   glGenFramebuffersEXT(1, &FBobject);
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBobject);
+
+   glGenRenderbuffersEXT(3, RBobjects);
+
+   glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[0]);
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
+
+   glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[1]);
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
+
+   glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[2]);
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT,
+                            Width, Height);
+
+   glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+                                GL_RENDERBUFFER_EXT, RBobjects[0]);
+   glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT,
+                                GL_RENDERBUFFER_EXT, RBobjects[1]);
+   glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
+                                GL_RENDERBUFFER_EXT, RBobjects[2]);
+
+   CheckError(__LINE__);
+}
+
+
+static GLuint
+LoadAndCompileShader(GLenum target, const char *text)
+{
+   GLint stat;
+   GLuint shader = glCreateShader_func(target);
+   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, "drawbuffers: problem compiling shader:\n%s\n", log);
+      exit(1);
+   }
+   return shader;
+}
+
+
+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, "drawbuffers: shader link error:\n%s\n", log);
+   }
+}
+
+
+static void
+SetupShaders(void)
+{
+   /* second color output = 1 - first color */
+   static const char *fragShaderText =
+      "void main() {\n"
+      "   gl_FragData[0] = gl_Color; \n"
+      "   gl_FragData[1] = vec4(1.0) - gl_Color; \n"
+      "}\n";
+
+   GLuint fragShader, program;
+
+   fragShader = LoadAndCompileShader(GL_FRAGMENT_SHADER, fragShaderText);
+   program = glCreateProgram_func();
+
+   glAttachShader_func(program, fragShader);
+   glLinkProgram_func(program);
+   CheckLink(program);
+   glUseProgram_func(program);
+}
+
+
+static void
+SetupLighting(void)
+{
+   static const GLfloat frontMat[4] = { 1.0, 0.5, 0.5, 1.0 };
+   static const GLfloat backMat[4] = { 1.0, 0.5, 0.5, 1.0 };
+
+   glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, frontMat);
+   glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, backMat);
+   glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 1);
+   glEnable(GL_LIGHT0);
+   glEnable(GL_LIGHTING);
+}
+
+
+static void
+Init(void)
+{
+   CheckExtensions();
+   GetExtensionFuncs();
+   SetupRenderbuffers();
+   SetupShaders();
+   SetupLighting();
+   glEnable(GL_DEPTH_TEST);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+   glutInit(&argc, argv);
+   glutInitWindowPosition(0, 0);
+   glutInitWindowSize(Width, Height);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
+   Win = glutCreateWindow(argv[0]);
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutDisplayFunc(Display);
+   Init();
+   glutMainLoop();
+   return 0;
+}