Rasterizer.h File Reference

3D triangle rasterizer function. More...

#include "ShaderParams.h"

Go to the source code of this file.

Macros
#define	TGX_RASTERIZE_SUBPIXEL_BITS   (6)
	Sub-pixel precision bits. More...

Functions
template<typename SHADER_FUNCTION , typename RASTERIZER_PARAMS >
void	tgx::rasterizeTriangle (const int LX, const int LY, const RasterizerVec4 &V0, const RasterizerVec4 &V1, const RasterizerVec4 &V2, const int32_t offset_x, const int32_t offset_y, const RASTERIZER_PARAMS &data, SHADER_FUNCTION shader_fun)
	Fast triangle rasterizer for 3D graphics: More...

Detailed Description

3D triangle rasterizer function.

Macro Definition Documentation

TGX_RASTERIZE_SUBPIXEL_BITS

#define TGX_RASTERIZE_SUBPIXEL_BITS   (6)

Sub-pixel precision bits.

Value should range between 1 and 8. Larger value provide greater resolution and smoother animation but at the expense of the maximum viewport size:

subpixel bits	max viewport size LX*LY
8	2048 x 2048
6	4096 x 4096
4	8192 x 8192
2	16384 x 16384

Function Documentation

rasterizeTriangle()

template<typename SHADER_FUNCTION , typename RASTERIZER_PARAMS >

void tgx::rasterizeTriangle	(	const int	LX,
		const int	LY,
		const RasterizerVec4 &	V0,
		const RasterizerVec4 &	V1,
		const RasterizerVec4 &	V2,
		const int32_t	offset_x,
		const int32_t	offset_y,
		const RASTERIZER_PARAMS &	data,
		SHADER_FUNCTION	shader_fun
	)

Fast triangle rasterizer for 3D graphics:

Features

• Pixel perfect rasterization with adjustable subpixels from 2 to 8 bits (set with TGX_RASTERIZE_SUBPIXEL_BITS).
  
• Top-left rule to prevent drawing pixels twice.
• Tile rasterization: large viewport can be splitted in multiple sub-images.
• templated shader functions so to implement: z-buffer testing, shading, texturing...

Template Parameters

SHADER_FUNCTION	the shader function to call.
RASTERIZER_PARAMS	the type of the object containing the 'uniform' data (ie data not specific to a vertex).

Parameters

LX,LY	Viewport size. The image itself may be smaller than the viewport and an offset may be specified so it is possible to draw the whole viewport in 'tile" mode be calling this method several times with different offsets. The maximum viewport size depend on TGX_RASTERIZE_SUBPIXEL_BITS
V0,V1,V2	Normalized coordinates of the vertices of the triangle (x,y,z,w) where, 'a la opengl' the viewport is mapped to [-1, 1]^2. These vectors also optionally contain the 'varying' parameters associated with each vertex, namely the texture coords and the color associated with each vertex (when applicable) that are used by the shader function.
offset_x,offset_y	Offset of this image inside the viewport. So the image corresponds to to the box [offset_x, offset_x + im.width[x[offset_x, offset_x + im.height[ and only the intersection of this box with the viewport box [0, LX[x[0, LY[ is drawn onto the image.
data	'Uniform' parameters (depending on the rasterization type).
shader_fun	the shader function. see Shaders.h for the implementation of classic shaders.

Remarks

• Maximum viewport size depending on TGX_RASTERIZE_SUBPIXEL_BITS:
  

  | subpixel bits | max viewport size LX*LY |
  |---------------|-------------------------|
  |      8        |      2048 x 2048        |
  |      6        |      4096 x 4096        |
  |      4        |      8192 x 8192        |
  |      2        |     16384 x 16384       |

• The (x,y) coordinates of the vertices V0,V1,V2 do not need to be inside the viewport [-1,1]^2 and yet the triangle will still be perfectly rasterized provided that they are not 'too far away'. This 'too far away' correspond to the maximum viewport size according to the chosen sub-pixel precision (for instance, [-2,2]^2 will work any viewport at most 1024x1024 when using 8 bits precision).
• Color are passed in RGBf format irrespectively of the image color type to improve quality and simplify handling of different image types.