add a vbo rectangle

1 files changed, 48 insertions, 16 deletions

diff --git a/vbo.c b/vbo.c
index 8a01251..dd1e429 100644
--- a/vbo.c
+++ b/vbo.c
@@ -34,6 +34,7 @@ typedef struct gltpoint
 int program_running = 1;
 SDL_Surface *screen;
 GLuint buffer_objects[3];
+GLuint buffer_objects2[3];
 
 /* few light arrays */
 const GLfloat fNoLight[]     = { 0.0f, 0.0f, 0.0f, 1.0f    };
@@ -57,25 +58,28 @@ static void setup_glew(void);
 static void setup_opengl(void);
 
 /* we have a separate buffer objects for vertex data, attributes, and indices
- * gl*Pointer gets assiociated with currently binded buffer
  * interleaved arrays improve cache performance, the key is locality
+ * for simplicity, vertex is composed of 3 components and texcoord of 2 components
  */
 static int gltGenVBOInterleaved(GLuint *bufferobjects, float *vert_arr,
            float *texcoord_arr, float *norm_arr, unsigned char *color_arr,
-           unsigned short *indices_arr, size_t points_n, size_t indices_n)
+           unsigned short *indices_arr, GLsizeiptr points_n, GLsizeiptr indices_n)
 {
-    /* skip error checks for now */
+    if (!bufferobjects || !vert_arr || !texcoord_arr || !norm_arr || !color_arr ||
+        !indices_arr || !points_n || !indices_n)
+        return -1;
 
     /* create an interleaved data structure, is it worth the cpu time? */
-    size_t attrib_buff_sz = ((points_n * (3+2) * sizeof(GLfloat)) +
-                             (points_n * 3 * sizeof(GLubyte)));
+    GLsizeiptr attrib_buff_sz = ((points_n * (3+2) * sizeof(GLfloat)) +
+                                 (points_n * 3 * sizeof(GLubyte)));
 
     if ((attrib_buff_sz % sizeof(gltpoint_t)) != 0)
     {
-        fprintf(stderr, "gltGenVBOInterleaved: fatal, gltpoint_t appears to be padded!\n");
-        exit(-1);
+        fprintf(stderr, "%s: fatal, gltpoint_t appears to be padded!\n", __FUNCTION__);
+        return -1;
     }
 
+    /* I call point a vbo slice */
     size_t slices_n = attrib_buff_sz / sizeof(gltpoint_t);
 
     gltpoint_t *gltpoints_arr = (gltpoint_t *) malloc(attrib_buff_sz);
@@ -83,7 +87,7 @@ static int gltGenVBOInterleaved(GLuint *bufferobjects, float *vert_arr,
     {
         fprintf(stderr, "%s failed, %s:%d\n", __FUNCTION__, __FILE__, __LINE__);
         perror("malloc");
-        exit(-1);
+        return -1;
     }
 
     /* build interleaved data structure, may not be cache friendly */
@@ -119,7 +123,7 @@ static int gltGenVBOInterleaved(GLuint *bufferobjects, float *vert_arr,
     return 0;
 }
 
-static int gltDrawVBOInterleaved(GLuint *bufferobjects, size_t indices_n)
+static int gltDrawVBOInterleaved(GLuint *bufferobjects, size_t indices_n, GLenum mode)
 {
     glEnableClientState(GL_VERTEX_ARRAY);
     glEnableClientState(GL_NORMAL_ARRAY);
@@ -139,7 +143,7 @@ static int gltDrawVBOInterleaved(GLuint *bufferobjects, size_t indices_n)
 
     /* indices data */
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bufferobjects[2]);
-    glDrawElements(GL_TRIANGLES, indices_n, GL_UNSIGNED_SHORT, 0);
+    glDrawElements(mode, indices_n, GL_UNSIGNED_SHORT, 0);
 
     glDisableClientState(GL_VERTEX_ARRAY);
     glDisableClientState(GL_NORMAL_ARRAY);
@@ -343,7 +347,8 @@ static void render(void)
         glPushMatrix();
             /* draw vbo */
             glTranslatef(0.0f, 0.0f, -4.0f);
-            gltDrawVBOInterleaved(buffer_objects, 3);
+            gltDrawVBOInterleaved(buffer_objects, 3, GL_TRIANGLES);
+            gltDrawVBOInterleaved(buffer_objects2, 4, GL_QUADS);
         glPopMatrix();
     }
     /* restore the matrix state */
@@ -361,7 +366,7 @@ static void setup_sdl(void)
         exit(-1);
     }
     atexit(SDL_Quit);
-    SDL_WM_SetCaption("SDL", NULL);
+    SDL_WM_SetCaption("VBO", NULL);
 
     SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
     SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
@@ -413,10 +418,10 @@ int main(int argc, char **argv)
     setup_opengl();
     gltErrorCheck();
 
-    /* setup a vbo */
+    /* setup a triangle */
     float vert_arr[9] = { 0.0f, 0.0f,  0.0f,
                           1.0f, 0.0f,  0.0f,
-                          0.5f, 0.66f, 0.0f };
+                          0.5f, 0.83f, 0.0f };
 
     float norm_arr[9] = { 0.0f, 0.0f, 1.0f,
                           0.0f, 0.0f, 1.0f,
@@ -432,8 +437,35 @@ int main(int argc, char **argv)
 
     unsigned short indices_arr[3] = { 0, 1, 2 };
 
-    gltGenVBOInterleaved(buffer_objects, vert_arr, texcoord_arr, norm_arr, color_arr,
-                    indices_arr, 3, 3);
+    gltGenVBOInterleaved(buffer_objects, vert_arr, texcoord_arr, norm_arr,
+                         color_arr, indices_arr, 3, 3);
+    gltErrorCheck();
+
+    /* setup a rectangle, notice the ccw winding */
+    float vert_arr2[12] = { -0.5f, 1.0f, 0.0f,
+                            -1.0f, 1.0f, 0.0f,
+                            -1.0f, 0.0f, 0.0f,
+                            -0.5f, 0.0f, 0.0f };
+
+    float norm_arr2[12] = { 0.0f, 0.0f, 1.0f,
+                            0.0f, 0.0f, 1.0f,
+                            0.0f, 0.0f, 1.0f,
+                            0.0f, 0.0f, 1.0f };
+
+    float texcoord_arr2[8] = { 0.5f, 0.0f,
+                               0.0f, 0.0f,
+                               0.0f, 1.0f,
+                               0.5f, 1.0f };
+
+    unsigned char color_arr2[12] = { 255, 0, 0,
+                                     0, 255, 0,
+                                     0, 0, 255,
+                                     255, 0, 255 };
+
+    unsigned short indices_arr2[4] = { 0, 1, 2, 3 };
+
+    gltGenVBOInterleaved(buffer_objects2, vert_arr2, texcoord_arr2, norm_arr2,
+                         color_arr2, indices_arr2, 4, 4);
     gltErrorCheck();
 
     while (program_running)