How can I speed up my VBO construction from model data

Graphics and GPU Programming Programming

Started by ashstampede April 10, 2008 03:58 AM

4 comments, last by rip-off 11 years, 2 months ago

124

Author

April 10, 2008 03:58 AM

I posted this originally in graphics and theory but doesnt seem to be getting a response. I have a section that will look through all the vertices,uv, normals and create Indices for them, But with larger objects Its really slow. I have this model that is 25K triangles or so and It took maybe 20mins and it didnt load unto the screen. I get setting a break point to see if it was still processing which is was. Models that are in the 500 area took 3-4 seconds from loading the mesh data from file and then building the VBO. With the larger model, loading the mesh data from file is pretty fast, fast enough for me. So its just the building of the VBO that seems to be the issuse. the original forum thread is here http://www.gamedev.net/community/forums/topic.asp?topic_id=490143

V-man

813

April 10, 2008 09:55 AM

Sounds like you are doing some processing work on the CPU that is taking a lot of time. Why don't you store the *needed* information in your file?
Just store the indices and then the vertex, normals, texcoords. Read from disk and shoot to GL.

Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);

Khaos Dragon

196

April 11, 2008 12:34 AM

Make a model loading function that checks to see if a 'cooked' version of the model is already cached on disk, if not.. it defaults to doing the cooking or processing you described above and then saves the cooked results to file so that upon the next load, you can avoid having to reprocess.

When uploading data from cooked binary data into your VBO's, you should just be able to blast through the data with a couple memcpy's.

Also if you are calling glMapBufferARB, make sure to invalidate the buffer by calling glBufferDataARB with a null pointer beforehand so that the driver knows it doesn't have to expend extra effort to maintain the state of whatever garbage data exists in the VBO.

V-man

813

April 11, 2008 08:08 AM

You could just call glBufferData with new data. The driver will allocate a new buffer. Eventually, the old buffer gets deleted by the driver. This was a recommendation in a PDF. Not usre if it was nvidia or ATI.

gboxentertainment

775

January 21, 2013 10:32 AM

[quote name='Khaos Dragon' timestamp='1207874055' post='4199747']

When uploading data from cooked binary data into your VBO's, you should just be able to blast through the data with a couple memcpy's.
[/quote]

I'm having trouble loading the data from my binary file after constructing it - shows up with a blank screen.


	int length;
	char* data;
	ifstream is;
	is.open("model.bin", ios::binary);
	is.seekg(0, ios::end);
	length = is.tellg();
	is.seekg(0, ios::beg);
	data = new char[length];
	is.read(data, length);
	is.close();

	glGenBuffers(1, &vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW);

How would I use memcpy to get this data into the buffer?