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Learning GL

Started by Hippokrates May 17, 2003 at 3:27 PM 5 replies 1k views

Original Post

May 17, 2003 at 3:27 PM

Let me first say that the goal of this post is definitely not to start the old DX vs. GL discussion again. I just have some questions about GL. 1) Is there any difference in speed between DX and OpenGL? 2) Does OpenGL have any kind of equivalent to DirectX''s (dynamic) vertex buffers? 3) Is there any equivalent to DirectX''s surfaces (for displaying large images that are not quadratic)?

JONSKI

May 17, 2003 at 8:08 PM

2) VBO perhaps? GL_ARB_vertex_buffer_object is the extension. As a rule of thumb, OpenGL gives the user more flexibility with storing vertex data.

3) I''m not familiar with DirectX''s surfaces, but perhaps they are like gluNurbs() or gluQuadric()

dede

May 18, 2003 at 12:12 AM

1) DirectX, fully optimized, is theoretically faster than OpenGL. Although in the short run, its easier,IMHO, to optimize OpenGL, because its structure is more like what a video card would see.

2) No Idea

3) (I''m assuming you mean raster screens) You can use Dynamic Textures, or glDrawPixel().

are you sure your using the word quadratic correctly?

Trienco

146

Trienco

May 18, 2003 at 4:41 AM

1) should probably pretty much depend on who''s programming it
2) above mentioned vertex_buffer_object (rather new extension)
3) i assume youre talking about textures that are no squares? there should be an extension. dont know if displaying images as such is possible at all.

Hippokrates

Author

Hippokrates

May 18, 2003 at 10:59 AM

1) Is the vertex_buffer_object extension supported by, say, a GeForce2 GTS ?
2) What are vertex arrays - or do they exist at all?
3) What I meant by ''surface'' is an image with width!=height and with width and height not being powers of 2.
For example a simple bitmap Image of 800*600 which I would be wanting to use for the title screen.

OrangyTang

333

OrangyTang

May 18, 2003 at 11:08 AM

quote:
Original post by Hippokrates
1) Is the vertex_buffer_object extension supported by, say, a GeForce2 GTS ?
2) What are vertex arrays - or do they exist at all?
3) What I meant by ''surface'' is an image with width!=height and with width and height not being powers of 2.
For example a simple bitmap Image of 800*600 which I would be wanting to use for the title screen.

1. Should be supported by all GeForce class cards. I wouldn''t be surprised to see TNTs supporting it as well.

2. Arrays of vertex data stored client-side (ie, system memory).

3. Theres an nVidia extension for that (GL_NV_texture_rectangle) which should be on most nVidia cards. I''ve also heard that Ati cards support it as well, but not having one i can''t give you any more info.

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