Create object shadows on big terrains

This code has been declared by its author to be Public Domain code.

Create object shadows on big terrains by Wiebo

2002

A function to let your world objects cast shadows on your terrain. The idea behind this function is simple, and it uses the ideas for realtime shadows by Norc. Thanks!

The trick though is to re-texture your terrain with your terrain lightmap, color all your shadow-casting objects black, roll them over, so we see them from the side and then do a renderworld. We then grab the rendered terrain + objects and copy it to the lightmap texture. This now contains the old lightmap + the dark versions of your objects.
Voila: instant shadows on terrain. Note that this method works best for static objects, like trees and buildings. It's not suited for realtime player and enemy shadows.

We then re-texture the terrain to see the results. The fun part is that it doesn't matter how many world objects you have, cos you only have to do it once, and you can even save the texture if you want to. (maybe use this in your world editor only?)

This is the function, simplified and stripped of misc settings which are for my game only. Make sure to hide all objects that do not need to cast shadows, like water, particles, player, etc

Function CreateShadowMap()

	; rotate world objects and color them black. you could also set entityalpha, obj\entity_near, 0.5

	 angle = 90		; adjust this according to your world time. 0 = noon, 90 = almost dark
		
	For obj.obj = Each obj
	
		RotateEntity obj\entity_near, 0, 0, angle, True
		EntityColor obj\entity_near, 0, 0, 0
		ShowEntity obj\entity_near
		EntityFX obj\entity_near, 1
	Next

	; texture terrain with lightmap, so we can grab it.
	TextureBlend world\texture1,1
	TextureBlend world\alphamap,1
	TextureBlend world\texture2,1
	TextureBlend world\lightmap,1
	EntityTexture world\terrain, world\lightmap, 0, 1
	
	; setup cam
	; make sure that camera is at correct height, so that terrain is in the middle of the screen.
	
	CameraFogMode world\camera, 0
	CameraRange world\camera, 1, 810
	PositionEntity heli\camerapivot, world\terrain_scale /4, 0, world\terrain_scale /4; middle of terrain
	RotateEntity world\camera, 90, 0, 0, True
	PositionEntity world\camera, -.05, 800, 0
	CameraZoom world\camera, 16

	; grab new texture. my terrain texture dimension is 512.
	
	RenderWorld()
	CopyRect (GraphicsWidth() / 2) - 256, (GraphicsHeight() / 2) - 256, 512,512, 0,0, BackBuffer(), TextureBuffer (world\lightmap)

	; restore obj settings
	
	For obj.obj = Each obj
		EntityColor obj\entity_near, 255,255,255
		EntityAlpha obj\entity_near, 1
		RotateEntity obj\entity_near, obj\pitch, obj\yaw, obj\roll		; get original rotational angles
	Next
	
	; restore terrain (with NEW shadowmap)
	TextureBlend world\texture1, 2
	TextureBlend world\alphamap, 2
	TextureBlend world\texture2, 3
	TextureBlend world\lightmap, 2
	EntityTexture world\terrain, world\texture1, 0, 0
	EntityTexture world\terrain, world\alphamap, 0, 1
	EntityTexture world\terrain, world\texture2, 0, 2
	EntityTexture world\terrain, world\lightmap, 0, 3

	; restore camera to original position
	; [code snipped]

End Function

Comments

MErren

2005

Nice, but where are the Type definitions
for World and obj ?
and how to use?

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