Software 3D Renderer

A simple OpenGL like software renderer written in BlitzBasic.

Highlights:

• Perspective projection
• Z-Buffering
• Supported Primitives: SR_POINTS, SR_LINES, SR_TRIANGLES
• Transformation: srRotate, srTranslate, srScale
• Lightning: SR_LIGHT1 (pointlight) is alway turned on.
• Shading: Flat shading (vertex normals currently ignored)

How to use

Copy renderer.bb and math.bb into you project's include folder and type include "renderer.bb". Switch to the graphics mode by call the Graphics command. Every call to the software renderer must made between srInit and srDestroy. Don't forget to call Flip every frame.

Screenshot

Flat Shading

Example

Example taken from triangle-example.bb. Renders a filled triangle.

Include "renderer.bb"

Graphics(800, 600, 0, 2)
SetBuffer BackBuffer()

srInit()

srMatrixMode(SR_PROJECTION)
srLoadIdentity()
srPerspective(1.0, Float(GraphicsWidth())/Float(GraphicsHeight()), 0.1, 100.0)
srDepthRange(0.0, 100.0)

srMatrixMode(SR_MODELVIEW)

While Not KeyDown(1)
	Cls()
	srLoadIdentity()
	srTranslate(0.0, 0.0, -2)
	
	srBegin(SR_TRIANGLES)
	srVertex( 0,  1, 0) ; Top Middle
	srVertex(-1, -1, 0) ; Bottom Left
	srVertex( 1, -1, 0) ; Bottom Right
	srEnd()

	Flip(0)
Wend

srDestroy()
End

Rendering pipeline

Rendering is allmost done in OpenGL style:

1. Eye coordinates = ModelView x Object coordinates
2. Eye normal = Inverse ModelView x Object normal coordinates
3. Clip coordinates = Projection matrix x Eye coordinates
4. Normalized device coordinates = Clip coordinates x, y, z / Clip w
5. View transformation
6. TempOriginX = Viewport width/2 + Viewport x
7. TempOriginY = Viewport height/2 + Viewport y
8. TempRangeHalf = (Depth range far - Depth range near)/2
9. Window X = Viewport width/2 * Device x + TempOriginX
10. Window Y = Viewport height/2 * Device y + TempOriginY
11. Window Z = TempRangeHalf*Device z + TempRangeHalf
12. Clear Z Buffer
13. Draw primitives in window coordinates. (Depth function is always set to GL_GREATER)