Fog

Hardware Fog API for the PowerVR More...

Files
file	pvr_fog.h
	Public API for the PVR's hardware fog.

Functions
void	pvr_fog_table_color (float a, float r, float g, float b)
	Set the table fog color.
void	pvr_fog_vertex_color (float r, float g, float b)
	Set the vertex fog color.
void	pvr_fog_far_depth (float d)
	Set the fog far depth.
void	pvr_fog_table_exp2 (float density)
	Initialize the fog table using an exp2 algorithm (like GL_EXP2).
void	pvr_fog_table_exp (float density)
	Initialize the fog table using an exp algorithm (like GL_EXP).
void	pvr_fog_table_linear (float start, float end)
	Initialize the fog table using a linear algorithm (like GL_LINEAR).
void	pvr_fog_table_custom (float *table)
	Set a custom fog table from float values.

Detailed Description

Hardware Fog API for the PowerVR

Todo

Explain fog modes + equations

Note

Thanks to Paul Boese for figuring this stuff out

Function Documentation

pvr_fog_far_depth()

void pvr_fog_far_depth

(

float

d

)

Set the fog far depth.

This function sets the PVR_FOG_DENSITY register appropriately for the specified value.

Parameters

d	The depth to set

pvr_fog_table_color()

void pvr_fog_table_color	(	float	a,
		float	r,
		float	g,
		float	b )

Set the table fog color.

This function sets the color of fog for table fog. 0-1 range for all colors.

Parameters

a	Alpha value of the fog
r	Red value of the fog
g	Green value of the fog
b	Blue value of the fog

pvr_fog_table_custom()

void pvr_fog_table_custom

(

float *

table

)

Set a custom fog table from float values.

This function allows you to specify whatever values you need to for your fog parameters. All values should be clamped between 0 and 1, and its your responsibility to set up the PVR_FOG_DENSITY register by calling pvr_fog_far_depth() with an appropriate value. The table passed in should have 129 entries, where the 0th entry is farthest from the eye and the last entry is nearest. Higher values = heavier fog.

Parameters

table

The table of fog values to set

See also

pvr_fog_table_exp2(), pvr_fog_table_exp(), pvr_fog_table_linear()

pvr_fog_table_exp()

void pvr_fog_table_exp

(

float

density

)

Initialize the fog table using an exp algorithm (like GL_EXP).

This function will automatically set the PVR_FOG_DENSITY register to 259.999999 as a part of its processing, then set up the fog table.

Parameters

density

Fog density value

See also

pvr_fog_table_exp2(), pvr_fog_table_linear(), pvr_fog_table_custom()

pvr_fog_table_exp2()

void pvr_fog_table_exp2

(

float

density

)

Initialize the fog table using an exp2 algorithm (like GL_EXP2).

This function will automatically set the PVR_FOG_DENSITY register to 259.999999 as a part of its processing, then set up the fog table.

Parameters

density

Fog density value

See also

pvr_fog_table_exp(), pvr_fog_table_linear(), pvr_fog_table_custom()

pvr_fog_table_linear()

void pvr_fog_table_linear	(	float	start,
		float	end )

Initialize the fog table using a linear algorithm (like GL_LINEAR).

This function will set the PVR_FOG_DENSITY register to the as appropriate for the end value, and initialize the fog table for perspectively correct linear fog.

Parameters

start	Fog start point
end	Fog end point

See also

pvr_fog_table_exp(), pvr_fog_table_exp2(), pvr_fog_table_custom()

pvr_fog_vertex_color()

void pvr_fog_vertex_color	(	float	r,
		float	g,
		float	b )

Set the vertex fog color.

This function sets the fog color for vertex fog. 0-1 range for all colors.

Parameters

r	Red value of the fog
g	Green value of the fog
b	Blue value of the fog