Using buffers

Graphics and GPU Programming Programming OpenGL

Started by SimonS January 20, 2009 10:32 AM

6 comments, last by V-man 15 years, 3 months ago

122

Author

January 20, 2009 10:32 AM

I have a problem when I use buffers to cash memory on GPU. The program crash with code: 0xC0000005 mNumIndices is 36 and mNumVertices is 24. Here´s my "bind" code:


	glGenBuffers(1, &mElemBuffer);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mElemBuffer );
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, mNumIndices * sizeof(GLuint),
                     mIndices, GL_STATIC_DRAW);

	glGenBuffers(1, &mArrBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, mElemBuffer );
	glBufferData(GL_ARRAY_BUFFER, mNumVertices * sizeof(GLfloat), mVertices,
                     GL_STATIC_DRAW);

	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0 );

When I draw my box I use this code:


	glBindBuffer(GL_ARRAY_BUFFER,	      mArrBuffer);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mElemBuffer);

        ...

	glDrawElements( GL_TRIANGLES, mNumIndices, GL_UNSIGNED_INT, mIndices );

	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

If I comment the two glBindBuffer before rendering, it works. But then I dont use the buffers. Hmm .. Please help me. New to OpenGL. Btw, its OpenGLES 2.0. But that doesnt matter I think. [Edited by - SimonS on January 20, 2009 10:59:13 AM]

KulSeran

3,272

January 20, 2009 11:08 AM

Quote:
glGenBuffers(1, &mArrBuffer);
glBindBuffer(GL_ARRAY_BUFFER, mElemBuffer );
glBufferData(GL_ARRAY_BUFFER, mNumVertices * sizeof(GLfloat), mVertices, GL_STATIC_DRAW);

Looks like a typo. You didn't bind your mArrBuffer.

My Blog

SimonS

122

Author

January 20, 2009 11:13 AM

Quote:Original post by KulSeran
Quote:
glGenBuffers(1, &mArrBuffer);
glBindBuffer(GL_ARRAY_BUFFER, mElemBuffer );
glBufferData(GL_ARRAY_BUFFER, mNumVertices * sizeof(GLfloat), mVertices, GL_STATIC_DRAW);

Looks like a typo. You didn't bind your mArrBuffer.

Thanks for answering.
I fixed that, but still the same problem :(

rozz666

896

January 20, 2009 11:19 AM

Quote:Original post by SimonS

	glDrawElements( GL_TRIANGLES, mNumIndices, GL_UNSIGNED_INT, mIndices );

Unless you choose some particular indices, you shuld pass NULL (or 0) as the last parameter when an index buffer is bound.

SimonS

122

Author

January 20, 2009 11:23 AM

Quote:Original post by rozz666
Quote:Original post by SimonS
	glDrawElements( GL_TRIANGLES, mNumIndices, GL_UNSIGNED_INT, mIndices );
Unless you choose some particular indices, you shuld pass NULL (or 0) as the last parameter when an index buffer is bound.

Okej, thanx. But the problem is still. I`ve fixed the two you mentioned.

V-man

813

January 20, 2009 11:48 AM

After you call
glBindBuffer(GL_ARRAY_BUFFER, mArrBuffer);
call glVertexPointer

example:
http://www.opengl.org/wiki/VBO#Sample_Code

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);

SimonS

122

Author

January 21, 2009 02:12 AM

Quote:Original post by V-man
After you call
glBindBuffer(GL_ARRAY_BUFFER, mArrBuffer);
call glVertexPointer

example:
http://www.opengl.org/wiki/VBO#Sample_Code

That function doesnt exist in OpenGLES 2.0. Cant get it to work.

V-man

813

January 21, 2009 09:12 AM

According to their specification (from khronos.org)

2.8 Vertex Arrays
you would have to use glVertexAtrribPointer
glEnableVertexAttribArray( uint index );
glDisableVertexAttribArray( uint index );

so glVertexPointer and the rest are killed off. Good idea.

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