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voodoo_john

OpenGL Thermal / Night Vision in OpenGL using Shaders

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Hi all, I''m an old man trying to learn new tricks. Recently I''ve began the process of introducing shaders to my engine using GL_ARB_VERTEX_SHADER. I don''t use CG at the moment because I''m doing a x-platform engine that must run on OS X. My questions is: using shader assembly, what would be the best way of doing a thermal or night vision viewing mode like in AVP2 say? I''m currently working on a Zombie game called ZOMBIE ISLAND an would like a night vision stylee mode, and infra-red/thermal one as well. Any help appreciated, John

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Well, I guess you need alpha/temperature maps to use as textures - the values in these maps are then used to index into a palette texture. The palette texture would contain smooth gradations of colour.

Now, I''m interested in this myself because, ugh, I work for a Thermal Imaging company and we are planning on moving over to pixel shaders for our temperature map palettization.

If anyone knows what the resulting ps program would look like - well, feel free to plant it here first

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I had thought along those lines, but that technique requires artists to have pre assigned temperature data to _every_ object in the scene. Surely this can be faked algorithmically? Does anyone know how they did it in AVP2 which has three separate vision modes?

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well, i dont know much about pixel shaders, but if you could calculate the depth of the object at each pixel you could set the color to something corresponding with that value multiplied with the temperature of the object, i think that should work out pretty nice.

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Aye, but again that would require artist intervention :-O I ain''t no artist....I''m sure there must be a way to fake it. Let''s forget characters just now, how would you have thermal vision for a world. You obviously wouldn''t want to assign temperature data to all objects in the world....

Anyone got any ideas about night-vision? In the recent thread on comemrcial source code, the source for Commanche Hookum seens to just blend a green quad over the screen...might give that a go :D


cheers !

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Guest Anonymous Poster
An easy way to fake it.. "Light" the model with a light source at the camera''s location, and then map different light levels to a 1d color scale texture (where "dark" is dark blue and "bright" is red/orange) in a pixel shader. This way the center of the model will have a hot color that fades out toward the edges. Scale the brightness based on the temperature of the object, so eg. a stone object looks colder than a human. This is basically a variation of the "iridescent" rendering demo you can find at the NVidia site.

Now that I think about it, you could probably just do this with a spherical environment map with a red dot in the middle fading to blue towards the edges. Doesn''t even require shaders.

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Guest Anonymous Poster
In spherical environment mapping, you generate texture coordinates based on the vertex normals. To put it simply, if a vertex (ie faces it connects to) is facing left you set the UV coordinates of the vertex to the left side of the texture, and if the vertex is facing the camera, the texture coordinates are somewhere in the middle. If the environment map texture is red in the middle and fades to dark blue on the edges, this will look a bit like "heat vision" especially if you blur the end result. (render to texture)

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Well, I''m thinking you need temperature maps if you want to do this correctly (they would just be luminance maps) - speaking as someone who works for an infrared thermography company!

I''m not sure how they did things in splinter cell however, which is a pretty nice representation in my opinion. Don''t forget that luminance maps for things like walls/floors will be more or less background noise, with a some features - its the hot things, like people, lights etc. that need the maps.

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Well, yeah, you don''t really need maps for EVERY object in the scene... You can have some algorithmic way of determining the heat of a ''non-heat-generating'' object by simply using a blue texture with some noise added in to break up the monotony. Now, for heat generating objects, I believe you would need to do it manually. Otherwise, how would a computer know that a human''s eyes are ''hotter'' than their feet? And to fake this, I think it would still be really hard to pull it off without some artist intervention.

Chris Pergrossi
My Realm | "Good Morning, Dave"

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