source: nanovis/trunk/RenderVertexArray.cpp @ 4794

Last change on this file since 4794 was 3611, checked in by ldelgass, 7 years ago

Use nv namespace for classes in nanovis rather than prefixing class names with
Nv (still need to convert shader classes).

  • Property svn:eol-style set to native
File size: 3.7 KB
Line 
1/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2/*
3 * ----------------------------------------------------------------------
4 *  Render to vertex array
5 *
6 *  This class implements "render to vertex array" functionality
7 *  using vertex and pixel buffer objects (VBO and PBO).
8 *
9 *  Operation:
10 *  1. A buffer object is created
11 *  2. The buffer object is bound to the pixel pack (destination) buffer
12 *  3. glReadPixels is used to read from the frame buffer to the buffer object
13 *  4. The buffer object is bound to the vertex array
14 *  5. Vertex array pointers are set
15 * 
16 *  Usage:
17 *  1. Create a floating point pbuffer
18 *  2. Create a RenderVertexArray object for each vertex attribute
19 *       you want to render to
20 *  3. Render vertex data to pbuffer using a fragment program (could
21 *       use multiple draw buffers here)
22 *  4. Call Read() method to read data from pbuffer to vertex array
23 *  5. Call SetPointer() method to set vertex array pointers
24 *  6. Set any other other static vertex array attribute pointers
25 *  7. Render geometry as usual using glDrawArrays or glDrawElements
26 *
27 * ======================================================================
28 *  AUTHOR:  Wei Qiao <qiaow@purdue.edu>
29 *           Purdue Rendering and Perceptualization Lab (PURPL)
30 *
31 *  Copyright (c) 2004-2013  HUBzero Foundation, LLC
32 *
33 *  See the file "license.terms" for information on usage and
34 *  redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
35 * ======================================================================
36 */
37#include <stdio.h>
38
39#include <GL/glew.h>
40#include <GL/gl.h>
41
42#include "RenderVertexArray.h"
43#include "Trace.h"
44
45using namespace nv;
46
47RenderVertexArray::RenderVertexArray(int nverts, GLint size, GLenum type) :
48    _usage(GL_STREAM_COPY_ARB),
49    _nverts(nverts), 
50    _size(size), 
51    _type(type)
52{
53    switch (_type) {
54    case GL_HALF_FLOAT_NV:
55        _bytesPerComponent = 2;
56        break;
57    case GL_FLOAT:
58        _bytesPerComponent = sizeof(float);
59        break;
60    default:
61        ERROR("unsupported RenderVertexArray type");
62        return;
63    }
64
65    // create the buffer object
66    glGenBuffersARB(1, &_buffer);
67    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, _buffer);
68    glBufferDataARB(GL_PIXEL_PACK_BUFFER_ARB, 
69                    _nverts*_size*_bytesPerComponent,
70                    0, _usage); // undefined data
71    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0);
72
73    // set equivalent image format
74    switch(_size) {
75    case 1:
76        _format = GL_LUMINANCE;
77        break;
78    case 3:
79        _format = GL_RGB;
80        break;
81    case 4:
82        _format = GL_RGBA;
83        break;
84    default:
85        ERROR("unsupported RenderVertexArray size");
86        return;
87    }
88}
89
90RenderVertexArray::~RenderVertexArray()
91{
92    glDeleteBuffersARB(1, &_buffer);
93}
94
95void
96RenderVertexArray::loadData(void *data)
97{
98    // load data to buffer object
99    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, _buffer);
100    glBufferDataARB(GL_PIXEL_PACK_BUFFER_ARB, 
101                    _nverts*_size*_bytesPerComponent,
102                    data, _usage);
103    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0);
104}
105
106void
107RenderVertexArray::read(int w, int h)
108{
109    // bind buffer object to pixel pack buffer
110    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, _buffer);
111
112    // read from frame buffer to buffer object
113    glReadPixels(0, 0, w, h, _format, _type, 0);
114
115    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0);
116}
117
118void
119RenderVertexArray::setPointer(GLuint index)
120{
121    // bind buffer object to vertex array
122    glBindBufferARB(GL_ARRAY_BUFFER_ARB, _buffer);
123    //glVertexAttribPointerARB(index, _size, _type, GL_FALSE, 0, 0);          //doesn't work
124    glVertexPointer(_size, _type, 0, 0);
125
126    glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
127}
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