GlPointSizePointerOES and glScalef

Question

I use point sprites to display several tens of thousands of points, each of which has a different size. It works well, looks great, and pretty fast. I use VBO with coordinates and sizes in it (4 floats per point).

Here is my display code

glEnable(GL_POINT_SPRITE_OES);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, pointTexture);
glTexEnvi( GL_POINT_SPRITE_OES, GL_COORD_REPLACE_OES, GL_TRUE );
glEnableClientState(GL_VERTEX_ARRAY);
glBindBuffer(GL_ARRAY_BUFFER, pointVertices);
glVertexPointer(3, GL_FLOAT, 4*sizeof(float), 0);
glEnableClientState(GL_POINT_SIZE_ARRAY_OES);
glPointSizePointerOES(GL_FLOAT,4*sizeof(float),(GLvoid*) (sizeof(GL_FLOAT)*3));
glDrawArrays(GL_POINTS, 0, pointNum);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glDisableClientState(GL_POINT_SIZE_ARRAY_OES);
glDisableClientState(GL_VERTEX_ARRAY);
glDisable(GL_TEXTURE_2D);
glDisable(GL_POINT_SPRITE_OES);

Now I would also like to zoom in, i.e. to use glScalef. Is it possible to resize points without updating VBO? glPointSizehas no effect as I use GL_POINT_SIZE_ARRAY_OES.

Answer 1

Yes, use glPointParameter with the GL_POINT_DISTANCE_ATTENUATION parameter.

http://www.khronos.org/opengles/sdk/1.1/docs/man/glPointParameter.xml

However, it’s quite difficult to get the right.