I have been trying to convert some intermediate terrain generating into VBO, I am just learning it but its producing unfavorable results.
I am not sure what to populate the index array with, or if i am populating it correctly via the offsets or if the size of the memory allocated is correct.
When i run the app, something shows up quickly add disappears,but it doesnt have the shape of the terrain. It sort of resembles a single triangle that is elongated as a huge plane.
I populate the index array with the vertices and normals like so
//vertex index offset
//vertices
unsigned int vertOffset = 0;
//normals
unsigned int normalOffset = totalVertices * 3;
/*ommited nested for loop going through z < height and x < width*/
//fill index buffer
//vertex
terrainIndexArray[vertOffset] = float(x);
terrainIndexArray[vertOffset+1] = y;
terrainIndexArray[vertOffset+2] = float(z);
vertOffset +=3;
//Normal
terrainIndexArray[normalOffset] = nodeNormal.x;
terrainIndexArray[normalOffset+1] = nodeNormal.y;
terrainIndexArray[normalOffset+2] = nodeNormal.z;
normalOffset +=3;
I am just using the actual point position and the normal, when i initialize the VBO it looks like this
totalVertices = length * width;
terrainVertices = new Vertex[totalVertices];
//terrainTextures = new TexUV[totalVertices];
//terrainColors = new Vertex[totalVertices];
terrainNormals = new Vector3D[totalVertices];
terrainIndexArray = new float[totalVertices * 6 * sizeof(float)];
//Create buffer object Arrays
glGenBuffersARB(currentVBOIndex,&terrainVBO);
glBindBufferARB(GL_ARRAY_BUFFER_ARB, terrainVBO);
nextVBOIndex();
// create a data store large enought for all but unInitialize
//We will give the same chunks over and over agian so we need them in app and gpu memory
glBufferDataARB(GL_ARRAY_BUFFER_ARB, totalVertices * 6 * sizeof(float),//3 vertices,3normals,3color 2 textures
NULL, GL_DYNAMIC_DRAW_ARB); //11
//Vertex data
glBufferSubDataARB(GL_ARRAY_BUFFER_ARB, 0,
totalVertices * 3 * sizeof(float), terrainVertices);
//Normals
glBufferSubDataARB(GL_ARRAY_BUFFER_ARB, totalVertices * 3 * sizeof(float),
totalVertices * 3 * sizeof(float), terrainNormals);
//index buffer
glGenBuffersARB(currentVBOIndex, &terrainIndexBO);
glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER, terrainIndexBO);
glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER,
totalVertices * 6 * sizeof(float),
terrainIndexArray, GL_DYNAMIC_DRAW_ARB);
nextVBOIndex();
When time to draw the data
glEnableClientState( GL_VERTEX_ARRAY ); // Enable Vertex Arrays
glEnableClientState( GL_NORMAL_ARRAY );
glEnableClientState( GL_INDEX_ARRAY );
if(GL_ARB_vertex_buffer_object)
{
glBindBufferARB( GL_ARRAY_BUFFER_ARB, terrainVBO );
//vertices
glVertexPointer( 3, GL_FLOAT, 0, BUFFER_OFFSET(0) ); // Set The Vertex Pointer To The Vertex Buffer
//Normals;
glNormalPointer(GL_FLOAT, 0, BUFFER_OFFSET(totalVertices * 3 * sizeof(float)) );
//index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, terrainIndexBO);
}
// Render
glDrawElements( GL_TRIANGLES,totalVertices * 6 * sizeof(float),GL_UNSIGNED_INT,terrainIndexArray); // Draw All Of The Triangles At Once
//unbinded
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
// Disable arrays
glDisableClientState( GL_VERTEX_ARRAY ); // Enable Vertex Arrays
glDisableClientState( GL_NORMAL_ARRAY );
// Enable Texture Coord Arrays
glDisableClientState( GL_INDEX_ARRAY );
