std::size_t VertexDataManager::writeAttributeData(ArrayVertexBuffer *vertexBuffer, GLint start, GLsizei count, const VertexAttribute &attribute, GLsizei instances)
{
Buffer *buffer = attribute.mBoundBuffer.get();
int inputStride = attribute.stride();
int elementSize = attribute.typeSize();
const FormatConverter &converter = formatConverter(attribute);
std::size_t streamOffset = 0;
void *output = NULL;
if (vertexBuffer)
{
output = vertexBuffer->map(attribute, spaceRequired(attribute, count, instances), &streamOffset);
}
if (output == NULL)
{
ERR("Failed to map vertex buffer.");
return -1;
}
const char *input = NULL;
if (buffer)
{
int offset = attribute.mOffset;
input = static_cast<const char*>(buffer->data()) + offset;
}
else
{
input = static_cast<const char*>(attribute.mPointer);
}
if (instances == 0 || attribute.mDivisor == 0)
{
input += inputStride * start;
}
if (converter.identity && inputStride == elementSize)
{
memcpy(output, input, count * inputStride);
}
else
{
converter.convertArray(input, inputStride, count, output);
}
vertexBuffer->unmap();
return streamOffset;
}
int elementsInBuffer(const VertexAttribute &attribute, int size)
{
int stride = attribute.stride();
return (size - attribute.mOffset % stride + (stride - attribute.typeSize())) / stride;
}
