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gallium: used inverted bitmap texture to simplify the fragment shader.

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"Off" bits get stored as texel=0xff and "on" bits get stored as texel=0x0.
Then use KIL -tmp to kill the off bits and keep the on bits.
This shortens the fragment program by two instructions.
This commit is contained in:
Brian
2008-03-31 15:12:14 -06:00
parent 23b03c536d
commit 6b0be38a6c
1 changed files with 20 additions and 29 deletions
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49
src/mesa/state_tracker/st_cb_bitmap.c
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@@ -59,6 +59,19 @@
/**
* glBitmaps are drawn as textured quads. The user's bitmap pattern
* is stored in a texture image. An alpha8 texture format is used.
* The fragment shader samples a bit (texel) from the texture, then
* discards the fragment if the bit is off.
*
* Note that we actually store the inverse image of the bitmap to
* simplify the fragment program. An "on" bit gets stored as texel=0x0
* and an "off" bit is stored as texel=0xff. Then we kill the
* fragment if the negated texel value is less than zero.
*/
/**
* The bitmap cache attempts to accumulate multiple glBitmap calls in a
* buffer which is then rendered en mass upon a flush, state change, etc.
@@ -102,7 +115,7 @@ make_bitmap_fragment_program(GLcontext *ctx)
if (!p)
return NULL;
p->NumInstructions = 5;
p->NumInstructions = 3;
p->Instructions = _mesa_alloc_instructions(p->NumInstructions);
if (!p->Instructions) {
@@ -121,33 +134,11 @@ make_bitmap_fragment_program(GLcontext *ctx)
p->Instructions[ic].TexSrcTarget = TEXTURE_2D_INDEX;
ic++;
/* SWZ tmp0.x, tmp0.x, 1111; # tmp0.x = 1.0 */
p->Instructions[ic].Opcode = OPCODE_SWZ;
p->Instructions[ic].DstReg.File = PROGRAM_TEMPORARY;
p->Instructions[ic].DstReg.Index = 0;
p->Instructions[ic].DstReg.WriteMask = WRITEMASK_X;
p->Instructions[ic].SrcReg[0].File = PROGRAM_TEMPORARY;
p->Instructions[ic].SrcReg[0].Index = 0;
p->Instructions[ic].SrcReg[0].Swizzle
= MAKE_SWIZZLE4(SWIZZLE_ONE, SWIZZLE_ONE, SWIZZLE_ONE, SWIZZLE_ONE );
ic++;
/* SUB tmp0, tmp0.wwww, tmp0.xxxx; # tmp0.w -= 1 */
p->Instructions[ic].Opcode = OPCODE_SUB;
p->Instructions[ic].DstReg.File = PROGRAM_TEMPORARY;
p->Instructions[ic].DstReg.Index = 0;
p->Instructions[ic].SrcReg[0].File = PROGRAM_TEMPORARY;
p->Instructions[ic].SrcReg[0].Index = 0;
p->Instructions[ic].SrcReg[0].Swizzle = SWIZZLE_WWWW;
p->Instructions[ic].SrcReg[1].File = PROGRAM_TEMPORARY;
p->Instructions[ic].SrcReg[1].Index = 0;
p->Instructions[ic].SrcReg[1].Swizzle = SWIZZLE_XXXX; /* 1.0 */
ic++;
/* KIL if tmp0 < 0 */
/* KIL if -tmp0 < 0 # texel=0 -> keep / texel=0 -> discard */
p->Instructions[ic].Opcode = OPCODE_KIL;
p->Instructions[ic].SrcReg[0].File = PROGRAM_TEMPORARY;
p->Instructions[ic].SrcReg[0].Index = 0;
p->Instructions[ic].SrcReg[0].NegateBase = NEGATE_XYZW;
ic++;
/* END; */
@@ -289,7 +280,7 @@ make_bitmap_texture(GLcontext *ctx, GLsizei width, GLsizei height,
for (col = 0; col < width; col++) {
/* set texel to 255 if bit is set */
destRow[comp] = (*src & mask) ? 255 : 0;
destRow[comp] = (*src & mask) ? 0x0 : 0xff;
destRow += cpp;
if (mask == 128U) {
@@ -311,7 +302,7 @@ make_bitmap_texture(GLcontext *ctx, GLsizei width, GLsizei height,
for (col = 0; col < width; col++) {
/* set texel to 255 if bit is set */
destRow[comp] =(*src & mask) ? 255 : 0;
destRow[comp] =(*src & mask) ? 0x0 : 0xff;
destRow += cpp;
if (mask == 1U) {
@@ -505,7 +496,7 @@ draw_bitmap_quad(GLcontext *ctx, GLint x, GLint y, GLfloat z,
static void
reset_cache(struct st_context *st)
{
memset(st->bitmap.cache->buffer, 0, sizeof(st->bitmap.cache->buffer));
memset(st->bitmap.cache->buffer, 0xff, sizeof(st->bitmap.cache->buffer));
st->bitmap.cache->empty = GL_TRUE;
st->bitmap.cache->xmin = 1000000;
@@ -642,7 +633,7 @@ accum_bitmap(struct st_context *st,
/* XXX try to combine this code with code in make_bitmap_texture() */
#define SET_PIXEL(COL, ROW) \
cache->buffer[py + (ROW)][px + (COL)] = 0xff;
cache->buffer[py + (ROW)][px + (COL)] = 0x0;
for (row = 0; row < height; row++) {
const GLubyte *src = (const GLubyte *) _mesa_image_address2d(unpack,