core  array_cache  math  swrast  swrast_setup  tnl  tnl_dd             

---

sw_span Struct Reference

Contains data for either a horizontal line or a set of pixels that are passed through a pipeline of functions before being drawn. More...

#include <s_context.h>

Data Fields
GLint	x
GLint	y
GLuint	start
	At this time, start is always zero. More...
GLuint	end
	At this time, start is always zero. More...
GLboolean	writeAll
	This flag indicates that mask[] array is effectively filled with ones. More...
GLenum	primitive
	either GL_POLYGON, GL_LINE, GL_POLYGON, GL_BITMAP. More...
GLuint	facing
	0 = front-facing span, 1 = back-facing span (for two-sided stencil). More...
GLuint	interpMask
	This bitmask (of SPAN_* flags) indicates which of the x/xStep variables are relevant. More...
GLfloat	red
GLfloat	redStep
GLfloat	green
GLfloat	greenStep
GLfloat	blue
GLfloat	blueStep
GLfloat	alpha
GLfloat	alphaStep
GLfloat	specRed
GLfloat	specRedStep
GLfloat	specGreen
GLfloat	specGreenStep
GLfloat	specBlue
GLfloat	specBlueStep
GLfixed	index
GLfixed	indexStep
GLfixed	z
GLfixed	zStep
GLfloat	fog
GLfloat	fogStep
GLfloat	tex [MAX_TEXTURE_COORD_UNITS][4]
GLfloat	texStepX [MAX_TEXTURE_COORD_UNITS][4]
GLfloat	texStepY [MAX_TEXTURE_COORD_UNITS][4]
GLfixed	intTex [2]
GLfixed	intTexStep [2]
GLfloat	dzdx
GLfloat	dzdy
GLfloat	w
GLfloat	dwdx
GLfloat	dwdy
GLfloat	drdx
GLfloat	drdy
GLfloat	dgdx
GLfloat	dgdy
GLfloat	dbdx
GLfloat	dbdy
GLfloat	dadx
GLfloat	dady
GLfloat	dsrdx
GLfloat	dsrdy
GLfloat	dsgdx
GLfloat	dsgdy
GLfloat	dsbdx
GLfloat	dsbdy
GLfloat	dfogdx
GLfloat	dfogdy
GLuint	arrayMask
	This bitmask (of SPAN_* flags) indicates which of the fragment arrays in the span_arrays struct are relevant. More...
span_arrays *	array
	We store the arrays of fragment values in a separate struct so that we can allocate sw_span structs on the stack without using a lot of memory. More...

---

Detailed Description

Contains data for either a horizontal line or a set of pixels that are passed through a pipeline of functions before being drawn.

The sw_span structure describes the colors, Z, fogcoord, texcoords, etc for either a horizontal run or an array of independent pixels. We can either specify a base/step to indicate interpolated values, or fill in arrays of values. The interpMask and arrayMask bitfields indicate which are active.

With this structure it's easy to hand-off span rasterization to subroutines instead of doing it all inline in the triangle functions like we used to do. It also cleans up the local variable namespace a great deal.

It would be interesting to experiment with multiprocessor rasterization with this structure. The triangle rasterizer could simply emit a stream of these structures which would be consumed by one or more span-processing threads which could run in parallel.

---

Field Documentation

GLfloat sw_span::alpha

GLfloat sw_span::alphaStep

struct span_arrays* sw_span::array

We store the arrays of fragment values in a separate struct so that we can allocate sw_span structs on the stack without using a lot of memory. The span_arrays struct is about 400KB while the sw_span struct is only about 512 bytes.

GLuint sw_span::arrayMask

This bitmask (of SPAN_* flags) indicates which of the fragment arrays in the span_arrays struct are relevant.

GLfloat sw_span::blue

GLfloat sw_span::blueStep

GLfloat sw_span::dadx

GLfloat sw_span::dady

GLfloat sw_span::dbdx

GLfloat sw_span::dbdy

GLfloat sw_span::dfogdx

GLfloat sw_span::dfogdy

GLfloat sw_span::dgdx

GLfloat sw_span::dgdy

GLfloat sw_span::drdx

GLfloat sw_span::drdy

GLfloat sw_span::dsbdx

GLfloat sw_span::dsbdy

GLfloat sw_span::dsgdx

GLfloat sw_span::dsgdy

GLfloat sw_span::dsrdx

GLfloat sw_span::dsrdy

GLfloat sw_span::dwdx

GLfloat sw_span::dwdy

GLfloat sw_span::dzdx

GLfloat sw_span::dzdy

GLuint sw_span::end

At this time, start is always zero.

GLuint sw_span::facing

0 = front-facing span, 1 = back-facing span (for two-sided stencil).

GLfloat sw_span::fog

GLfloat sw_span::fogStep

GLfloat sw_span::green

GLfloat sw_span::greenStep

GLfixed sw_span::index

GLfixed sw_span::indexStep

GLuint sw_span::interpMask

This bitmask (of SPAN_* flags) indicates which of the x/xStep variables are relevant.

GLfixed sw_span::intTex[2]

GLfixed sw_span::intTexStep[2]

GLenum sw_span::primitive

either GL_POLYGON, GL_LINE, GL_POLYGON, GL_BITMAP.

GLfloat sw_span::red

GLfloat sw_span::redStep

GLfloat sw_span::specBlue

GLfloat sw_span::specBlueStep

GLfloat sw_span::specGreen

GLfloat sw_span::specGreenStep

GLfloat sw_span::specRed

GLfloat sw_span::specRedStep

GLuint sw_span::start

At this time, start is always zero.

GLfloat sw_span::tex[MAX_TEXTURE_COORD_UNITS][4]

GLfloat sw_span::texStepX[MAX_TEXTURE_COORD_UNITS][4]

GLfloat sw_span::texStepY[MAX_TEXTURE_COORD_UNITS][4]

GLfloat sw_span::w

GLboolean sw_span::writeAll

This flag indicates that mask[] array is effectively filled with ones.

GLint sw_span::x

GLint sw_span::y

GLfixed sw_span::z

GLfixed sw_span::zStep

---

The documentation for this struct was generated from the following file:

• s_context.h

---