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Case

Slowdown Problem

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Hi, I''m having a slowdown problem with my renderer: at some viewpoints the framerate drops dramatically for no apparent reason. I am drawing the entire map every frame and hence I''m sending the same amount of data to opengl (using nvidea vars) no matter what the viewpoint (no frustum culling.) When the entire map is visible the framerate is fine, it''s also fine when the camera is relatively close to the geometry or looking out across it and hence only showing part of the map, but at certain viewpoints a little further away but still not showing the whole map (often looking down on the level) the framerate literally halves. I am at a loss as to the cause of this. If anyone has experienced a similar problem, or has any suggestions on what might be causing it, please reply... It''s starting to bug me. Thanks in advance, Case.

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You might find it''s just a problem of fill rate. Todays cards often implement their own optimisations so that polygons off screen aren''t drawn or calculated. If you move back a little, more has to be drawn. Also remeber that if, from your view point, the world just happnes to be drawn from furthurest polygon to nearest. It''s going to draw everything. But if it draws from nearest to furthurest, it wont write to memory what is behind the first drawn polys. If this makes sence, then I commend you . These may be contributing to the slowdown, although for it to half the framerate is a little drastic. You must be drawing A LOT of polygons! Or it may just be a driver issue.

One by one, the peguins steal my sanity.

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I thought about fill rate, but the problem persists at low resolutions as well. And I don''t think it''s the number of polys either, cos the frame rate is fine when I have the entire map on screen and the problem occurs with small maps as well - perversly it''s when less polys are on screen that it slows down. Furthermore, the the same thing happens when I just dump the whole map out from vertex arrays in texture order, and when I draw it front to back from a bsp tree. It''s weird.

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