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what is the cost of unrendered geometry?...


Ok, lets say I am making a cliff / rock wall from lots of instances (lets say 8 different models instanced a 1000 or so times). These models are quite spherical and are rotated in every which direction, and are intersecting all over the place. Is there much of a rendering performance cost associated with doing things this way? as there will be a whole lot of geometry on the backfaces etc that never get fully rendered. (lets say 90% of the total polycount isn't visible to the camera). Is it a bad idea to do things this way? will the geo that isn't seen by the camera even have a cost to rendering that is worth worrying about? (only faces will be non visible to camera, not whole objects, so i guess they wont get occluded)

is there a link to any docs that cover this? i read the deferred rendering overview but it didn't really answer my questions. Any info will be greatly appreciated :) cheers

Product Version: UE 4.7
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asked Jun 16 '15 at 02:06 PM in Rendering

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avatar image Jacky Jun 16 '15 at 04:56 PM

In average how many polygons per mesh are you talking about? The whole mesh gets rendered unless all of it is occluded, so it may become a problem if those meshes have tens of thousands of polygons each.

avatar image Beddall Jun 17 '15 at 04:03 PM

lets say 5000 poly's per mesh (1000 meshes) But, don't materials etc only get rendered for each pixel that can be seen by the camera? surely geo that isnt seen would get rendered super quick in the geo pass of the rendering? and wouldn't even contribute to the other render passes as the renderer at this point has determined that they arent visible,and so no materials, lights etc get rendered on them... or is this over simplifying it?

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