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Code archives/3D Graphics - Effects/Simple shadows

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

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Simple shadows by nawi2007
This is a simple shadow system I made for fun. It's not that fast, and alpha shadows don't work properly.. but you might learn something from this.

Pic:
Graphics3D 800,600,0,2
SetBuffer BackBuffer()


Global Cam = CreateCamera()
MoveEntity Cam,0,5,-2



NewObject = GetObject()



;Position our entity
MoveEntity NewObject,0,2.5,0

;White plane
Plane = CreatePlane()
EntityColor Plane,255,255,255
MoveEntity Plane,0,-0.01,0

;Create light
Light = CreateSphere(5)
Spot = CreateLight(2,Light)
ScaleEntity Light,0.1,0.1,0.1
EntityColor Light,255,255,0



Repeat
	;Camera movement
	If KeyDown(200) Then MoveEntity Cam,0,0,1
	If KeyDown(208) Then MoveEntity Cam,0,0,-1
	If KeyDown(203) Then MoveEntity Cam,-1,0,0
	If KeyDown(205) Then MoveEntity Cam,1,0,0


	;Shadow object must be created and destroyed every frame
	Shadow = CreateMesh()
	
	EntityAlpha Shadow,1 
	;There is sadly a bug with alpha shadows.. Didn't figure out a proper solution to this one
	;You could use a camera, but would be a major slowdown
	
;	EntityColor Shadow,0,0,0
	

	;Light movement
	GY# = 7+Sin(MilliSecs()/10)*0.5
	GX# = Cos(MilliSecs()/10)*3
	
	;Draw shadow
	DrawShadow(NewObject,GX#,GY#,GZ#,Shadow)
	PositionEntity Light,GX#,GY#,GZ#
	
	
	;FPS
	FPSC=FPSC+1
	If MilliSecs()>FPSTimer+999 Then
		FPSTimer = MilliSecs()
		FPS=FPSC
		FPSC=0
	EndIf
	
	


	RenderWorld

	Text 0,0,"FPS: " + FPS
	;Text 0,20,"Trisrendered: " + TrisRendered()
	Flip 0

	;Destroy shadow
	FreeEntity Shadow

Until KeyHit(1)

Function DrawShadow(Entity,SX#,SY#,SZ#,Shadow)
	;This works by looping through all triangles, then calculating a line for each vertex to ground (y=0)

	EX#=EntityX#(Entity,1)
	EY#=EntityY#(Entity,1)
	EZ#=EntityZ#(Entity,1)
	ShadowSurface = CreateSurface(Shadow)
	Surfaces=CountSurfaces(Entity)
	For s=1 To Surfaces
		Surface = GetSurface(Entity,s)
		

		Triangles=CountTriangles(Surface)-1
		For t=0 To Triangles
			v1 = TriangleVertex(Surface,t,0)
			v2 = TriangleVertex(Surface,t,1)
			v3 = TriangleVertex(Surface,t,2)
			
			v1X# = VertexX#(Surface,v1)+EX#
			v1Y# = VertexY#(Surface,v1)+EY#
			v1Z# = VertexZ#(Surface,v1)+EZ#
			K#=-SY#/(SY#-v1Y#)
			v1XR# = SX# + (SX#-v1X#)*K#
			v1ZR# = SZ# + (SZ#-v1Z#)*K#

			v2X# = VertexX#(Surface,v2)+EX#
			v2Y# = VertexY#(Surface,v2)+EY#
			v2Z# = VertexZ#(Surface,v2)+EZ#
			K#=-SY#/(SY#-v2Y#)
			v2XR# = SX# + (SX#-v2X#)*K#
			v2ZR# = SZ# + (SZ#-v2Z#)*K#
			
			v3X# = VertexX#(Surface,v3)+EX#
			v3Y# = VertexY#(Surface,v3)+EY#
			v3Z# = VertexZ#(Surface,v3)+EZ#
			K#=-SY#/(SY#-v3Y#)
			v3XR# = SX# + (SX#-v3X#)*K#
			v3ZR# = SZ# + (SZ#-v3Z#)*K#
			
			;Backface culling works by calculating a camera vector and a surface normal
			;If the dot product is > 0 then draw
			
			;Camera vector
			CX#=SX#-(v1X#+v2X#+v3X#)*0.33333
			CY#=SY#-(v1Y#+v2Y#+v3Y#)*0.33333
			CZ#=SZ#-(v1Z#+v2Z#+v3Z#)*0.33333
			
			;Surface normal, create 2 vectors and then create vector W from their cross product
			UX# = V2X#-V1X#
			UY# = V2Y#-V1Y#
			UZ# = V2Z#-V1Z#
			VX# = V3X#-V1X#
			VY# = V3Y#-V1Y#
			VZ# = V3Z#-V1Z#
			WX# = UY#*VZ#-UZ#*VY#
			WY# = -(UX#*VZ#-UZ#*VX#)
			WZ# = UX#*VY#-UY#*VX#
			
			;Add triangle
			If (SY#>v1Y#) And (SY#>v2Y#) And (SY#>v3Y#) And (CX#*WX#+CY#*WY#+CZ#*WZ#)>0.0 Then
				AddTriangle(ShadowSurface,AddVertex(ShadowSurface,v1XR#,0,v1ZR#),AddVertex(ShadowSurface,v2XR#,0,v2ZR#),AddVertex(ShadowSurface,v3XR#,0,v3ZR#))
			EndIf

		Next
	Next
End Function

;Create a test object
Function GetObject()
	NewObject = CreateMesh()
	Cube = CreateCube()
	ScaleMesh Cube,0.6,2.5,0.6
	
	PositionMesh Cube,-3,0,3
	AddMesh Cube,NewObject
	
	PositionMesh Cube,6,0,0
	AddMesh Cube,NewObject
	
	PositionMesh Cube,-6,0,-6
	AddMesh Cube,NewObject
	
	PositionMesh Cube,6,0,0
	AddMesh Cube,NewObject
	
	Sphere = CreateSphere(16)

	
	PositionMesh Sphere,-3,2.5,3
	AddMesh Sphere,NewObject

	PositionMesh Sphere,6,0,0
	AddMesh Sphere,NewObject
	
	PositionMesh Sphere,-6,0,-6
	AddMesh Sphere,NewObject
	
	PositionMesh Sphere,6,0,0
	AddMesh Sphere,NewObject
	
	FreeEntity Cube
	FreeEntity Sphere
	
	EntityColor NewObject,0,200,0
	Return NewObject
End Function

Comments

Kryzon2008
Neat! Did you test it with animated meshes?


Dabhand2008
Thats pretty good nawi! :)


Nate the Great2008
I doesn't work when I use rotateentity() but it works when I use turnmesh().

Why could that be?


Stevie G2008
Replace this ..

v1X# = VertexX#(Surface,v1)+EX#
			v1Y# = VertexY#(Surface,v1)+EY#
			v1Z# = VertexZ#(Surface,v1)+EZ#
			K#=-SY#/(SY#-v1Y#)
			v1XR# = SX# + (SX#-v1X#)*K#
			v1ZR# = SZ# + (SZ#-v1Z#)*K#

			v2X# = VertexX#(Surface,v2)+EX#
			v2Y# = VertexY#(Surface,v2)+EY#
			v2Z# = VertexZ#(Surface,v2)+EZ#
			K#=-SY#/(SY#-v2Y#)
			v2XR# = SX# + (SX#-v2X#)*K#
			v2ZR# = SZ# + (SZ#-v2Z#)*K#
			
			v3X# = VertexX#(Surface,v3)+EX#
			v3Y# = VertexY#(Surface,v3)+EY#
			v3Z# = VertexZ#(Surface,v3)+EZ#
			K#=-SY#/(SY#-v3Y#)
			v3XR# = SX# + (SX#-v3X#)*K#
			v3ZR# = SZ# + (SZ#-v3Z#)*K#


With this ...

TFormPoint VertexX( Surface, v1 ), VertexY( Surface, v1 ) , VertexZ( Surface, v1 ) , Entity, 0
v1X# = TFormedX()
v1Y# = TFormedY()
v1Z# = TFormedZ()
K#=-SY#/(SY#-v1Y#)
v1XR# = SX# + (SX#-v1X#)*K#
v1ZR# = SZ# + (SZ#-v1Z#)*K#

TFormPoint VertexX( Surface, v2 ), VertexY( Surface, v2 ) , VertexZ( Surface, v2 ) , Entity, 0
v2X# = TFormedX()
v2Y# = TFormedY()
v2Z# = TFormedZ()
K#=-SY#/(SY#-v2Y#)
v2XR# = SX# + (SX#-v2X#)*K#
v2ZR# = SZ# + (SZ#-v2Z#)*K#

TFormPoint VertexX( Surface, v3 ), VertexY( Surface, v3 ) , VertexZ( Surface, v3 ) , Entity, 0
v3X# = TFormedX()
v3Y# = TFormedY()
v3Z# = TFormedZ()
K#=-SY#/(SY#-v3Y#)
v3XR# = SX# + (SX#-v3X#)*K#
v3ZR# = SZ# + (SZ#-v3Z#)*K#


Will ensure it works when using rotateentity.

Stevie


Ben(t)2008
edit: nevermind


Ryudin2008
Very nice!


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