Add shadow to buildings

[schedul-xor]

Since buildings are a kind of polygons, it should be possible to add shadows by tracing well known techniques (for example "shadow mapping"). It will be nice to add a directional light using the sun's ray.

TL;DR

I've tried shadow mapping implementation, but it's not finished. I think I'm almost there, but I need help.

Not-finished product (INTENSE FLASHING CAUTION): schedul-xor@2c6294b
(To run the product, (1) rewrite vtm-playground/build.gradle mainClassName = "org.oscim.test.SimpleMapTest" (2) ./gradlew :vtm-playground:run)

My strategy

It was to integrate this technology. Depth packing functions are (almost) copied from this page.

What I've done:

• Copy the source of OffscreenRenderer, rename it to ShadowRenderer.
• Build an orthogonal projection matrix, because it's a directional light.
• Build shadow map texture by rendering "building" polygons (actually the depth) to the frame buffer.
• Read the shadow texture from frame buffer and render the final shadow.

As a result

I succeeded to render shadow map, but failed to render the final shadow.

Problems

• Shadow maps are flashing. It should affect to the shadow rendering. Why flashing? Double buffering not working correctly?
• Buildings are expected to be rendered twice (first when building shadow map, second when rendering directly), but the second rendering failed unless mRenderer.update() was called. I'm not sure why.
• I've prepared 800x800 plane to check if it works, checked out that it works, but not sure why 800 is enough.
• The final shadow is not rendered. Where did I mistake?
• I've been working on this for eight days, but no progress. It's nearly uncontrollable. This feature needs technical support.

[Gustl22]

Thanks @schedul-xor: Gettin closer :)

[Gustl22]

We have to clarify some design decisions (checkout my branch):
Since shadow feature (ShadowRenderer) is much more dependent on the ExtrustionRenderer than other Renderers we have the following options:

1. Extend ShadowRenderer from ExtrusionRenderer and decouple BuildingRenderer from ExtrusionRenderer, so depending on wether the shadow is activated use the one of them. (seems difficult, and needs setters)
2. provide setters in ExtrusionRenderer to be more flexible with ShadowRenderer and must of course be synchronized.
3. fully integrate shadow feature in ExtrusionRenderer with clearly distinguishable on/off toggle. (simplest solution)

Second solution, is the one of schedul-xor and mine. But there are these bugs to solve:

• the tiles have to be released to remove flickering, so we have to use the commonly render(GLViewport viewport) and use following setters.
• setter for current shader
• setter for usage of light
• setter for light to shadowMap matrix

[devemux86]

A user intuitive solution would be to toggle on/off the shadows without changing renderer classes.

Something like the current extrusion height change happening nicely in real time (#462).

[Gustl22]

As said...without modyfing the ExtrusionRenderer, wouldn't be possible (at least the setters).

[schedul-xor]

ShadowRenderer is currently depending on ExtrusionRenderer, but is probably expected to stand on it's own feet in the future. Building polygons are currently generated only from extrusion, and is better to leave room for improvement ... for example, to support additional 3d polygon data (using com.badlogic.gdx.graphics.g3d.model.*) later. Extending ExtrusionRenderer, in my opinion, is not a good idea.

How about adding multiple "Shadowable renderer" to ShadowRenderer, and let ExtrusionRenderer implement "Shadowable renderer" interfaces?

Can ExtrusionRenderer be used only as a rule-based 3d polygon generator? Actually it currently is, but it also contains complex building shaders.

[Gustl22]

How about adding multiple "Shadowable renderer" to ShadowRenderer, and let ExtrusionRenderer implement "Shadowable renderer" interfaces?

Can be possible, but would only be a more abstract version of a fully integration of shadow into ExtrusionRenderer. I will try out some constellation and can discuss them on PR :)

Can ExtrusionRenderer be used only as a rule-based 3d polygon generator?

Would be a good approach, to isolate rendering from the shaders and have a more modular / customizable ExtrusionRenderer...

[devemux86]

After latest merges, what is the state of this feature?

[devemux86]

Closed via #668.

[devemux86]

Another sample of the nice work and the library's power: