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InsaneX

A Bunch of Questions

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Sorry if these are stupid of have already been answered 1. I was was wondering if there is anything in OpengGL comparable to DirectX Point Sprites and indexed arrays 2. Also, DirectX can do software vertex processing? Does OpenGL have this capability? 3. I you had a game engine, would it make more sense to put all or your triangles into and array and use GL_TRIANGLES or use an algorithm of some sort to do a series of triangle strips? 4. Are BSP''s, quadtrees, and octrees fundamentally the same thing, with just a different number of "nodes". Or is there something different about their implementations (I''m pretty sure quadtrees, and octrees are the same. 5. I have also heard that BSP''s and the like aren''t going to be used much anymore, I think the big culling method is Portals. Is this true and are there any more major culling methods that would be worth it to look into. 6. I recently downloaded the quake demos, and noticed the dynamic lights cast from a rocket or bullet. How is this done? I was thinking lightmaps but I''m not sure. 7. How do you handle more than one texture with vertex arrays or VBO''s. Other than putting all the textures into a giant texture map, is there another way? 8. For a particle system, would it make sense to load all the verts into an array every frame for them to be displayed? Would you then use quads ( i don''t see how you could use triangle strips if they are put into an array). 9. Does anyone know a good tutorial on desiging and OpenGL graphics engine? 10.For displaying models and dynamic items in an engine, would you draw the level, translate to each model/items space and display with each item/model having its own array? Is switching arrays a fast operation? Is this just one of the billion ways to do it or is there a "proven" way. I am really sorry about the length, I have been saving these questions for awhile, Thanks for all your help in advance!

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quote:
Original post by InsaneX
Sorry if these are stupid of have already been answered
1. I was was wondering if there is anything in OpengGL comparable to DirectX Point Sprites and indexed arrays



You can switch to Ortho mode and draw in pixel coords. You can create sprites with textures.

quote:

2. Also, DirectX can do software vertex processing? Does OpenGL have this capability?



Yes OpenGL has Vertex Arrays.

quote:

3. I you had a game engine, would it make more sense to put all or your triangles into and array and use GL_TRIANGLES or use an algorithm of some sort to do a series of triangle strips?



Yeah put everything in vertex arrays and compile them into display lists. Make sure you have an algorithm that sorts the vertex arrays to do the Z-buffering yourself.

quote:

4. Are BSP''s, quadtrees, and octrees fundamentally the same thing, with just a different number of "nodes". Or is there something different about their implementations (I''m pretty sure quadtrees, and octrees are the same.



They have examples of this at gametutorials.com. Specific tutorials that do BSPs. If you buy the CD you get an octree example.

quote:

5. I have also heard that BSP''s and the like aren''t going to be used much anymore, I think the big culling method is Portals. Is this true and are there any more major culling methods that would be worth it to look into.



Don''t know.

quote:

6. I recently downloaded the quake demos, and noticed the dynamic lights cast from a rocket or bullet. How is this done? I was thinking lightmaps but I''m not sure.



Check out devmaster.net I think I saw a good tutorial about this topic there.

quote:

7. How do you handle more than one texture with vertex arrays or VBO''s. Other than putting all the textures into a giant texture map, is there another way?



There are actually texture arrays too.

quote:

8. For a particle system, would it make sense to load all the verts into an array every frame for them to be displayed? Would you then use quads ( i don''t see how you could use triangle strips if they are put into an array).



I think triangles are used to make the complex poly structures. I think it makes LOD calcs faster.

Like I said, use vertex arrays and compile them into display lists. As long as they aren''t animated you shouldn''t have to recalculate each time. Make sure they are grouped by magnitude or something similar.

quote:

9. Does anyone know a good tutorial on desiging and OpenGL graphics engine?



Nehe.gamedev.net and gametutorials.com have really good information about this.

quote:

10.For displaying models and dynamic items in an engine, would you draw the level, translate to each model/items space and display with each item/model having its own array? Is switching arrays a fast operation? Is this just one of the billion ways to do it or is there a "proven" way.



OpenGL has a projection matrix and a modelview matrix. With this it also has a stack. So you can glPushMatrix(); glTranslatef(); glRotatef(); and then glPopMatrix(); for each model/item you draw.

quote:

I am really sorry about the length, I have been saving these questions for awhile, Thanks for all your help in advance!


No problem. Waiting for Linae to get out of class so we can go home and she can tell me about her game industry class. The CCO of Amaze Entertainment will be in her class in a few weeks to talk about the industry and maybe he can get me a game QA/Programming job. That would be cool!

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