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authorKeith Packard <keithp@keithp.com>2002-05-13 07:55:48 +0000
committerEric Anholt <eric@anholt.net>2007-01-09 11:20:38 -0800
commit6633f3924d6f224d02f48808b28981f9775f6e72 (patch)
treef966d88a8e3fa3fc26c092d0743627360ca317bc
parent7ff23a96aaafb598a413e2bd4c52da98dfb8da4a (diff)
Update spec to match current implementation.
-rw-r--r--renderproto.txt159
1 files changed, 145 insertions, 14 deletions
diff --git a/renderproto.txt b/renderproto.txt
index bba445f..908b4f9 100644
--- a/renderproto.txt
+++ b/renderproto.txt
@@ -28,6 +28,12 @@ This extension was the work of many people, in particular:
+ Jon Leech, Brad Grantham and Allen Akin for patiently explaining
how OpenGL works.
+ + Carl Worth for providing the sample implementation of
+ trapezoid rendering
+
+ + Sam Pottle and Jamey Sharp for helping demonstrate the correctness
+ of the trapezoid specification.
+
3. Rendering Model
Render provides a single rendering operation which can be used in a variety of
@@ -154,7 +160,7 @@ DITHERINFO [
height: CARD16
]
-FIXED 32-bit value (top 24 are integer portion, bottom 8 are fraction)
+FIXED 32-bit value (top 16 are integer portion, bottom 16 are fraction)
POINTFIX [
x, y: FIXED
]
@@ -177,8 +183,12 @@ QUAD [
TRIANGLE [
p1, p2, p3: POINTFIX
]
+LINEFIX [
+ p1, p2: POINTFIX
+ ]
TRAP [
- top, bottom: SPANFIX
+ top, bottom: FIXED
+ left, right: LINEFIX
]
COLORTRIANGLE [
p1, p2, p3: COLORPOINT
@@ -264,6 +274,24 @@ come from the following table:
---
+Here are the disjoint and conjoint operators which need to be
+factored into the table above
+
+ Disjoint Conjoint
+ Fa Fb Fa Fb
+(0,0,0,0) 0 0 0 0
+(0,A,0,A) 1 0 1 0
+(0,0,B,B) 0 1 0 1
+(0,A,B,A) 1 min((1-a)/b,1) 1 max(1-a/b,0)
+(0,A,B,B) min((1-b)/a,1) 1 max(1-b/a,0) 1
+(0,0,0,A) max(1-(1-b)/a,0) 0 min(1,b/a) 0
+(0,0,0,B) 0 max(1-(1-a)/b,0) 0 min(a/b,1)
+(0,A,0,0) min(1,(1-b)/a) 0 max(1-b/a,0) 0
+(0,0,B,0) 0 min(1,(1-a)/b) 0 max(1-a/b,0)
+(0,0,B,A) max(1-(1-b)/a,0) min(1,(1-a)/b) min(1,b/a) max(1-a/b,0)
+(0,A,0,B) min(1,(1-b)/a) max(1-(1-a)/b,0) max(1-b/a,0) min(1,a/b)
+(0,A,B,0) min(1,(1-b)/a) min(1,(1-a)/b) max(1-b/a,0) max(1-a/b,0)
+
Saturate matches GL with FUNC_ADD, SRC_ALPHA_SATURATE, ONE, except
that it uses premultiplied alphas while GL uses non-premultiplied alphas.
@@ -307,16 +335,25 @@ in the general compositing operator along with a supplied source image:
tmp = Rasterize (polygon)
Composite (op, dst, src, tmp)
-When rasterized with Sharp edges, the mask is generated by setting pixels
-inside the polygon to 1 and pixels outside the mask to 0.
+When rasterized with Sharp edges, the mask is computed with a depth of 1 so
+that all of the mask values are either 0 or 1.
When rasterized with Smooth edges, the mask is generated by creating a square
around each pixel coordinate and computing the amount of that square covered
-by the polygon. Yes, this ignores sampling theory but it provides a precise
+by the polygon. This ignores sampling theory but it provides a precise
definition which is close to the right answer. This value is truncated to
the alpha width in the fallback format before application of the compositing
operator.
+---
+
+This needs rewriting to match current trapezoid specification and
+base other polygons on that. I suspect imprecise polygons will need
+to have a relaxed specification as well; hardware is unlikely to
+meet the "sum to one" constraint.
+
+---
+
When rasterized in Precise mode, the pixelization will match this
specification exactly.
@@ -686,12 +723,30 @@ Trapezoids
src: PICTURE
src-x, src-y: INT16
dst: PICTURE
+ mask-format: PICTFORMAT or None
traps: LISTofTRAP
- This request rasterizes the list of trapezoids. For each span, the
- left coordinate must be less than or equal to the right coordinate.
- The y coordinate of the top span must be less than or equal to the
- y coordinate of the bottom span. Results are undefined otherwise.
+ This request rasterizes the list of trapezoids. For each trap, the
+ area between the left and right edges is filled from the top to the
+ bottom. src-x and src-y register the pattern to the floor of the
+ top x and y coordinate of the left edge of the first trapezoid, they
+ are adjusted for subsequent trapezoids so that the pattern remains
+ globally aligned within the destination.
+
+ When mask-format is not None, trapezoids are rendered in the
+ following way with the effective mask computed in mask-format:
+
+ tmp = temporary alpha picture (in mask-format)
+ Combine (Zero, tmp, tmp, None)
+ for each trapezoid
+ Combine (Add, tmp, trapezoid, None)
+ Combine (op, dst, source, tmp)
+
+ When mask-format is None, trapezoids are rendered in the order
+ specified directly to the destination:
+
+ for each trapezoid
+ Combine (op, dst, source, trapezoid)
Triangles
@@ -699,17 +754,34 @@ Triangles
src: PICTURE
src-x, src-y: INT16
dst: PICTURE
- traps: LISTofTRIANGLE
+ mask-format: PICTFORMAT or None
+ triangles: LISTofTRIANGLE
This request rasterizes the list of triangles in the order they
occur in the list.
+ When mask-format is not None, triangles are rendered in the
+ following way with the effective mask computed in mask-format:
+
+ tmp = temporary alpha picture (in mask-format)
+ Combine (Zero, tmp, tmp, None)
+ for each trapezoid
+ Combine (Add, tmp, trapezoid, None)
+ Combine (op, dst, source, tmp)
+
+ When mask-format is None, triangles are rendered in the order
+ specified directly to the destination:
+
+ for each trapezoid
+ Combine (op, dst, source, trapezoid)
+
TriStrip
op: PICTOP
src: PICTURE
src-x, src-y: INT16
dst: PICTURE
+ mask-format: PICTFORMAT or None
points: LISTofPOINTFIX
Triangles are formed by initially using the first three points and
@@ -717,11 +789,27 @@ TriStrip
the list. If fewer than three points are provided, this request does
nothing.
+ When mask-format is not None, triangles are rendered in the
+ following way with the effective mask computed in mask-format:
+
+ tmp = temporary alpha picture (in mask-format)
+ Combine (Zero, tmp, tmp, None)
+ for each trapezoid
+ Combine (Add, tmp, trapezoid, None)
+ Combine (op, dst, source, tmp)
+
+ When mask-format is None, triangles are rendered in the order
+ specified directly to the destination:
+
+ for each trapezoid
+ Combine (op, dst, source, trapezoid)
+
TriFan
op: PICTOP
src: PICTURE
src-x, src-y: INT16
dst: PICTURE
+ mask-format: PICTFORMAT or None
points: LISTofPOINTFIX
Triangles are formed by initially using the first three points and
@@ -729,17 +817,26 @@ TriFan
int the list. If fewer than three points are provided, this request
does nothing.
-???
+ When mask-format is not None, triangles are rendered in the
+ following way with the effective mask computed in mask-format:
-Should I bother with these two compressed triangle representations?
+ tmp = temporary alpha picture (in mask-format)
+ Combine (Zero, tmp, tmp, None)
+ for each trapezoid
+ Combine (Add, tmp, trapezoid, None)
+ Combine (op, dst, source, tmp)
-???
+ When mask-format is None, triangles are rendered in the order
+ specified directly to the destination:
+
+ for each trapezoid
+ Combine (op, dst, source, trapezoid)
ColorTrapezoids
op: PICTOP
dst: PICTURE
- triangles: LISTofCOLORTRAP
+ trapezoids: LISTofCOLORTRAP
The geometry of the trapezoids must meet the same requirements as
for the Trapezoids request. The trapezoids are filled in the order
@@ -962,3 +1059,37 @@ CompositeGlyphs32
for each glyph
Combine (op, dst, source, glyph)
+14. Extension Versioning
+
+The Render extension was developed in parallel with the implementation to
+ensure the feasibility of various portions of the design. As portions of
+the extension are implemented, the version number of the extension has
+changed to reflect the portions of the standard provied. This document
+describes the intent for version 1.0 of the specification, the partial
+implementations have version numbers less than that. Here's a list of
+what each version before 1.0 implemented:
+
+ 0.0:
+ No disjoint/conjoint operators
+ No component alpha
+ Composite
+ CreateGlyphSet
+ FreeGlyphSet
+ AddGlyphs
+ CompositeGlyphs
+
+ 0.1:
+ Component alpha
+ FillRectangles
+
+ 0.2:
+ Disjoint/Conjoint operators
+
+ 0.3:
+ FreeGlyphs
+
+ 0.4:
+ Trapezoids
+ Triangles
+ TriStrip
+ TriFan