Horde3D

Is there a way to project a texture from a light as a light gobo.I understand I would need to create a custom light shader and modify calcPhongSpotLight in fragLighting.glsl. how would I go about generating the uv coordinates needed for the texture2D lookup (is the shadowMats useful here or only in dealing with shadow maps.
otherwise it would appear that using just the lightDir and the pos won't be enough determine the uv coordinates

Im a bit of beginner still at horde and dealing with shading so Im a little rusty on some of the matrix maths surrounding what need to be done

The easiest thing you can do is using a cube map as your projective texture which you just sample using the light vector as input. You can even apply an old trick from UE3 and use two cube maps between which you lerp based on distance. This can fake some nice soft shadows.

Thats an interesting one I hadn't considered using cubemaps. Do I have a way of orientating the light vector or am I limited to using the cubemap in world space?

marciano: yeah I remember that:

http://www.youtube.com/watch?v=Plnh28ykavQ

About 1:12 into the video is the cube map shadow example.

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-Alex
Website

Yes, marciano is right - it very easy way to render them to use cubemaps. You can try to search phoenix64 modifications of Horde engine in University of Augsburg SVN of Horde3D - he implemented cubemap shadows - you can try this method but using textured projection the same way like shadow. But I dont have nothing in my head how to make textured spot lights. May be you can try the same method as shadow mapping like with cubemap technique.
Yeah, cubemaps are good, but rendering each face independently not good... Sometimes it may become not nice bottleneck. It would be better to try Virtual Depth Shadow Textures technique, but I don't know how good it would be to use with textured lights... It is a nice try to inspect how it works with VSDT technique.
Sometimes I hate this advice, but... Another technique is for DX10 and higher hardware - to use Geometry Shaders and Instancing. Render all cubemap faces with Geometry Shader with one draw call, and Instancing when there are a lot of cubemaps(draw all of them one draw call).

Update:
Branch SVN is here and phoenix64 experiments also here: http://mm-werkstatt.informatik.uni-augs ... /branches/

Wait... someone actually still knows that code?

Don't expect anything good in there. Well, textured spot lights actually shouldn't be difficult either, the same principles still apply, only you use a different projection matrix for texture coords of your light texture.

Dual-paraboloid shadow mapping is what you're after if 6 draw passes to 6 different sides of a cube is a bit too hardcore and you don't have access to geometry shaders. This will bring the passes down to 2. And if this is too much and you don't mind major artefacts, there's this technique to bring it down to 1 pass:

http://www.gamedev.net/community/forums ... _id=517022

Edit: actually the "minor" artefacts are quite major...

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-Alex
Website

MistaED, I don't know exactly about Dual-paraboloid shadow mapping technique, I heard only that it works only with Forward Rendering. Techniques says "NO!" to Deferred Shading(info from Shiskovtsov 2005 - GPU Gems 2 - Deferred Shading on S.T.A.L.K.E.R.) I am Deferred Shading-man But thanks for the link to this good topic on gamedev!

I think this is might be a method to get textured lights without a cubemap (slide 13) but requires the view matrix and projection matrix of the light in order to use texture2DProj.

http://www.csee.wvu.edu/~tmcgraw/cs570s ... ture12.pdf

The stalker guys said that quite a while ago, and things have changed a bit since then.

In particular, they were worried about artefacts arising from the post-vertex transform linear-space interpolation (which is incorrect in a paraboloid space). You can solves this by correcting for it in the pixel shader, see here http://osman.brian.googlepages.com/dpsm.pdf

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Tristam MacDonald - [swiftcoding]