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dyerseve

drawrangeelements creating giving access violation reading 0x0000

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My code is something like:

vector<float> allvertexdata;
vector<int> allindexdata;

//... fill in the two buffers ...

if (allindexdata.size()*4!=totalISize) return false;
if (allvertexdata.size()*4!=totalVSize) return false;

nmesh.dbg_indexdata=allindexdata;
nmesh.dbg_vertexdata=allvertexdata;

glGenBuffersARB(1,&nmesh.VertexBuffer);
glBindBufferARB(GL_ARRAY_BUFFER,nmesh.VertexBuffer);
glBufferDataARB(GL_ARRAY_BUFFER,totalVSize,&allvertexdata[0],GL_STATIC_DRAW_ARB);

glGenBuffersARB(1,&nmesh.IndexBuffer);
glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB,nmesh.IndexBuffer);	
glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB,totalISize,&allindexdata[0],GL_STATIC_DRAW_ARB);	

glBindBufferARB(GL_ARRAY_BUFFER_ARB,0);
glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB,0);	


//... do some other initialization stuff ...


//... start rendering:
const char* ptrbase=0;

glBindBufferARB(GL_ARRAY_BUFFER,m.VertexBuffer);
glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB,m.IndexBuffer);	
		
glDisableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);	
glNormalPointer(m.ptrNormalSize,m.ptrNormalStride,ptrbase+m.ptrNormalOffset);
for (int i=0;i<8;i++) {
	glClientActiveTextureARB(GL_TEXTURE0_ARB+i);
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}

glEnableClientState(GL_VERTEX_ARRAY);	
glVertexPointer(m.ptrVertexSize,m.ptrVertexFormat,m.ptrVertexStride,ptrbase+m.ptrVertexOffset);

for (vector<CBatch>::const_iterator bit=m.batches.begin();bit!=m.batches.end();bit++) {

	if (0) {
		glBegin(GL_TRIANGLES);
		char* dbgvbase=(char*)&m.dbg_vertexdata[0];
		for (int i=bit->indexStart;i!=bit->indexEnd;i++) {
			int v=m.dbg_indexdata[i];		
			glColor4f(1.0f,3.0f,3.0f,1.0f);
			Vector3* dn=(Vector3*)(dbgvbase +  v*m.ptrNormalStride + m.ptrNormalOffset);
			glNormal3f(dn->x,dn->y,dn->z);
			Vector3* dv=(Vector3*)(dbgvbase +  v*m.ptrVertexStride + m.ptrVertexOffset);
			glVertex3f(dv->x,dv->y,dv->z);
		}
		glEnd();
	} else {
		glDrawRangeElements(GL_TRIANGLES,bit->vertexStart,bit->vertexEnd,bit->indexCount,GL_UNSIGNED_INT,ptrbase+bit->indexStart*4);
	}
}

The code works fine when I change the 0 to a 1 and use the glBegin stuff instead of the glDrawRangeElements command. When I used glDrawRangeElements, I get an access violation reading 0x00000000. The last pointer passed into it is null, but shouldn't glDrawRangeElements treat that as an index into the element buffer? Basically, I expect glDrawRangeElements to work exactly the way the code above it does (just more efficiently), but for some reason it doesn't work the way I think it should. Also vertexStart and vertexEnd should to the minimum and maximum index referred to by any of the indices right? (or is vertexStart something that is added to all of the indices?) Any ideas?

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