Changes between Version 41 and Version 42 of tutorial

Timestamp:

Jul 1, 2013, 2:40:59 AM (12 years ago)

Author:

leon

Comment:

Point cloud revised

tutorial

@@ -650 +650 @@
    Verify that there are no compile problems and that the {{{main()}}} contains {{{read_wavefront("motorBike.obj");}}}. 
    Disable lengthy wavefront saving in {{{main()}}}.
- 2. Instead of drawing of the teapot in {{{display()}}} we will draw single vertex array object as a point cloud with 
-  {{{
-  #!c
-   //glutSolidTeapot(0.6);
-   glDrawArrays(GL_POINTS, 0, vertices);
-  }}}
-  To be able to draw this, we need to prepare Vertex Array Object and buffer with {{{init();}}} that is called from {{{main()}}} just before {{{glutMainLoop();}}}
-  {{{
-  #!c
-void init()
-{
-  GLuint VAO[1];
-  GLuint Buffer[1];
-  glGenVertexArrays(1, VAO);
-  glBindVertexArray(VAO[0]);
-  glGenBuffers(1, Buffer);
-  glBindBuffer(GL_ARRAY_BUFFER, Buffer[0]);
-  glBufferData(GL_ARRAY_BUFFER, vertices*3*sizeof(GLfloat),
-               vertex, GL_STATIC_DRAW);
-  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
-  glEnableVertexAttribArray(0);
-}
-}}}
+ 2. Instead of drawing of the teapot in {{{display()}}} we will draw single vertex array object as a point cloud with adding
+  {{{
+  #!c
+  //glutSolidTeapot(0.6);
+  glVertexPointer(3, GL_FLOAT, 0, vertex);
+  glEnableClientState(GL_VERTEX_ARRAY);
+  glDrawArrays(GL_POINTS, 0, vertices);
+  glDisableClientState(GL_VERTEX_ARRAY);
+  }}}
+  that pushes 132871 vertices (1.5MB) from client memory to GPU on every redraw. Better approach would be to follow VBOs principles by generating vertex buffer in GPU as {{{temperature.c}}} example. 
  3. We see that rotation of the motorbike around the front wheel is not really nice. 
    To compensate we translate all points in the {{{vertex_shader[]}}} by adding {{{vec3(-0.75, 0, -0.7);}}}