Iterate over all point light sources in a single pass

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sasmaster
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Joined: Sun Jun 27, 2021 4:09 pm

Iterate over all point light sources in a single pass

Post by sasmaster »

Hi.
I am implementing custom PBR shading with point light sources. I took GLTF2/PBR sample material as the base.
So far I have been able to guess most of the Ogre's material semantics myself, but here's one thing I can understand:

I created 3 point light source in the scene. Inside gLTF2_PBR.material there is a standard parameter:

Code: Select all

        param_named_auto u_LightDirection light_position  0
        param_named_auto u_LightDirection1 light_position 1
        param_named_auto u_LightDirection1 light_position 2
     
My interpretation of is: "light_position" is the position of light source with the index 0 , 1 ,2 in the array of lights.

But in reality I see my assumption is wrong. Once I start moving any of the 3 lights in the scene around 3d model, I am getting switch from one source position to another which is a function of light's location. E.g, moving light#0 along Z performs correct shading of the surface till it gets to a distance of 100 units from the center ,than it stops working, and the direction of light#1 which was located closer to the surface takes effect. If I leave only one light source in the scene, it works perfectly.

I found it the docs this:
iteration once
The pass is only executed once which is the default behaviour.

iteration once\_per\_light point
The pass is executed once for each point light.

iteration 5
The render state for the pass will be setup and then the draw call will execute 5 times.

iteration 5 per\_light point
The render state for the pass will be setup and then the draw call will execute 5 times. This will be done for each point light.

iteration 1 per\_n\_lights 2 point
I tried the last one (which I assumed to be getting all the light sources in one pass),but it doesn't change.

So here is my question: How do I iterated over all the light source in a single pass shader program? I have 3 point lights in the scene.

Thanks.







Thanks!
paroj
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Re: Iterate over all point light sources in a single pass

Post by paroj »

sasmaster wrote: Tue Jun 29, 2021 8:56 am My interpretation of is: "light_position" is the position of light source with the index 0 , 1 ,2 in the array of lights.
this is correct. However, the array is sorted by distance to camera each frame. There is no easy way to identify a specific light due to this - you will have to compute lighting for all of them for consistent results.

The light iteration stuff you found in the docs considers multi-pass rendering.
sasmaster
Gnoblar
Posts: 9
Joined: Sun Jun 27, 2021 4:09 pm

Re: Iterate over all point light sources in a single pass

Post by sasmaster »

you will have to compute lighting for all of them for consistent results.
Yeah, once I connected all the lights into shading function, it all started working well.

Thanks for your attention!
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