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About psquare

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  1. I use ogre. Its a render to texture render target with rgba components. Each component is a float32. So total of 32x4 = 128 bits precision.
  2. Thanks for your reply. However, my question is more geared towards why this really happens.
  3. I am trying to recover position and normals from depth stored in render to texture. I store the depth like so in the render to texture:   VS:   outObjPosViewSpace = mul(worldView, inPos);   PS:   float depth = length(inObjPosViewSpace); // stored in component w of rgba texture   I am trying to recover the normals/depth like so:       float fDepth = tex2D(rtt, screenCoords).w;     float3 vPosition = eyePosW.xyz + viewRay*fDepth;       float3 vNormal = cross(normalize(ddy(vPosition.xyz)), normalize(ddx(vPosition.xyz)));     vNormal= normalize(vNormal);   The depth as read from the texture, and hence the recovered normals/positions show banding/artifacts. See images (trying to render swimming pool and also trying to recover pool bottom position for caustics). I am unsure why this banding occurs.   [url=http://postimg.org/image/9fgxqvqaz/][/url] [url=http://postimg.org/image/ybadedcyz/][/url] [url=http://postimg.org/image/wsez9e6ej/][/url] [url=http://postimg.org/image/lim9eg1d7/][/url]   I tried/read several things. For example:   http://www.gamedev.net/topic/480031-world-space---view-space-transformation/ http://mynameismjp.wordpress.com/2010/03/ -It does not matter whether I use 16 bit rgba for the rtt or 32 bit rgba -Filtering mode does not cause any changes.   As a side note, I was playing around in Vision Engine's vForge editor, and when I debugged the normals/depth by outputting same values to the shader as mine, I get similar artifacts and banding. I would assume that VE is doing correct math, since their deferred renderer is 'battle tested'.
  4. Voxel / Marching Cubes

    [quote] 1. How is Voxel data usually stored? Is it similar to height-mapped terrain where you can just specify heights and then generate the vertices during run-time? [/quote] It could be as simple as a raw 3D array with an associated value. This value can be density (e.g. 0 for air, 1 for solid), or multiple values like density, opacity, material id, etc. It depends on what all scalar quantities you need to represent in the 3D structure. Marching cubes 'walks' this volume and generates meshes which is what you render with ultimately. [quote] 2. How is the large memory footprint handled in a real-time simulation? Are there "chunks" which can be streamed in and out depending on view distance? [/quote] A voxel based data structure can run time compress/decompress the stored values using an algorithm like rle, etc, so that run time memory consumption is kept at a minimum. If RAM is not an issue, just disk space, then merely zipping up the raw serialized voxel data suffices. [quote] 3. What sort of partitioning/culling methods can apply? Octree/Frustum, Occlusion Culling? [/quote] This is sort of orthogonal to voxel/marching cubes, but you can use any method. It depends on what you want really/application domain. For example, in medical applications, you can't really use occlusion culling, because the volumes' color may need to be alpha blended with volumes occluding them. Usually however, if you have multiple volumes, at a minimum, you would do view frustum culling. [quote] 4. What sort of LOD techniques work well? (This could kind of apply to question 2 I guess) 5. Know of any simple examples I can examine? [/quote] PolyVox is a very good library that is used to work with voxel data. There's a lot of information on all of your above questions on the forums there. [url="http://www.thermite3d.org/phpBB3/"]http://www.thermite3d.org/phpBB3/[/url] C4 engine is another: [url="http://www.terathon.com/c4engine/index.php"]http://www.terathon....ngine/index.php[/url]
  5. Any approximation which looks convincing for the materials at hand, is good enough. There doesn't even have to be a physical basis for it. For example, this rather old demo: [url="http://www.youtube.com/watch?v=92bIPSh6r6Y"]http://www.youtube.c...h?v=92bIPSh6r6Y[/url] Just uses an N.V term for the lighting and some other neat tricks. I also would recommend slapping on some fresnel term (or some equivalent of it thereof) in any lighting model that you end up using. In my experience you can simulate a lot of materials by just tweaking the fresnel terms. (For example, rim lighting for a skin shader)
  6. OpenGL Theory to a Good Renderer

    Scene management, transformation hierarchies, etc are something that lie outside the scope of a renderer, in terms of a design. Like a wrapper. I think for your renderer, you should try to emulate the capabilities of OpenGL first (however minimal) You can then add a layer on top of your renderer that encapsulates logical/spatial grouping, scene management, etc and forwards draw calls to your renderer.
  7. Calculating Irradiance

    Typically you deal with normalized values (0 to 1), so in most apps you just tweak the light and/or materials to achieve the desired effect/lighting/shading. To actually use values like 60W, you have to do the computation with these 'physically correct' values and use hdr or a variation of it to map the values (may well be outside 0 to 1) back to 0 to 1. Another approach is to not use the actual physical values again, but to use a fake multiplier for your really intense lights and just tweak it along with the hdr
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