s_stencil.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

/*
 * Mesa 3-D graphics library
 * Version:  7.1
 *
 * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


#include "glheader.h"
#include "context.h"
#include "imports.h"

#include "s_context.h"
#include "s_depth.h"
#include "s_stencil.h"
#include "s_span.h"



/* Stencil Logic:

IF stencil test fails THEN
   Apply fail-op to stencil value
   Don't write the pixel (RGBA,Z)
ELSE
   IF doing depth test && depth test fails THEN
      Apply zfail-op to stencil value
      Write RGBA and Z to appropriate buffers
   ELSE
      Apply zpass-op to stencil value
ENDIF

*/


/**
 * Apply the given stencil operator to the array of stencil values.
 * Don't touch stencil[i] if mask[i] is zero.
 * Input:  n - size of stencil array
 *         oper - the stencil buffer operator
 *         face - 0 or 1 for front or back face operation
 *         stencil - array of stencil values
 *         mask - array [n] of flag:  1=apply operator, 0=don't apply operator
 * Output:  stencil - modified values
 */
static void
apply_stencil_op( const GLcontext *ctx, GLenum oper, GLuint face,
                  GLuint n, GLstencil stencil[], const GLubyte mask[] )
{
   const GLstencil ref = ctx->Stencil.Ref[face];
   const GLstencil wrtmask = ctx->Stencil.WriteMask[face];
   const GLstencil invmask = (GLstencil) (~wrtmask);
   const GLstencil stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
   GLuint i;

   switch (oper) {
      case GL_KEEP:
         /* do nothing */
         break;
      case GL_ZERO:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  stencil[i] = 0;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  stencil[i] = (GLstencil) (stencil[i] & invmask);
	       }
	    }
	 }
	 break;
      case GL_REPLACE:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  stencil[i] = ref;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  GLstencil s = stencil[i];
		  stencil[i] = (GLstencil) ((invmask & s ) | (wrtmask & ref));
	       }
	    }
	 }
	 break;
      case GL_INCR:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  GLstencil s = stencil[i];
		  if (s < stencilMax) {
		     stencil[i] = (GLstencil) (s+1);
		  }
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  /* VERIFY logic of adding 1 to a write-masked value */
		  GLstencil s = stencil[i];
		  if (s < stencilMax) {
		     stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s+1)));
		  }
	       }
	    }
	 }
	 break;
      case GL_DECR:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  GLstencil s = stencil[i];
		  if (s>0) {
		     stencil[i] = (GLstencil) (s-1);
		  }
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  /* VERIFY logic of subtracting 1 to a write-masked value */
		  GLstencil s = stencil[i];
		  if (s>0) {
		     stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s-1)));
		  }
	       }
	    }
	 }
	 break;
      case GL_INCR_WRAP_EXT:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  stencil[i]++;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil s = stencil[i];
                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s+1)));
	       }
	    }
	 }
	 break;
      case GL_DECR_WRAP_EXT:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  stencil[i]--;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil s = stencil[i];
                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s-1)));
	       }
	    }
	 }
	 break;
      case GL_INVERT:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  GLstencil s = stencil[i];
		  stencil[i] = (GLstencil) ~s;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
		  GLstencil s = stencil[i];
		  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & ~s));
	       }
	    }
	 }
	 break;
      default:
         _mesa_problem(ctx, "Bad stencil op in apply_stencil_op");
   }
}




/**
 * Apply stencil test to an array of stencil values (before depth buffering).
 * Input:  face - 0 or 1 for front or back-face polygons
 *         n - number of pixels in the array
 *         stencil - array of [n] stencil values
 *         mask - array [n] of flag:  0=skip the pixel, 1=stencil the pixel
 * Output:  mask - pixels which fail the stencil test will have their
 *                 mask flag set to 0.
 *          stencil - updated stencil values (where the test passed)
 * Return:  GL_FALSE = all pixels failed, GL_TRUE = zero or more pixels passed.
 */
static GLboolean
do_stencil_test( GLcontext *ctx, GLuint face, GLuint n, GLstencil stencil[],
                 GLubyte mask[] )
{
   GLubyte fail[MAX_WIDTH];
   GLboolean allfail = GL_FALSE;
   GLuint i;
   GLstencil r, s;
   const GLuint valueMask = ctx->Stencil.ValueMask[face];

   ASSERT(n <= MAX_WIDTH);

   /*
    * Perform stencil test.  The results of this operation are stored
    * in the fail[] array:
    *   IF fail[i] is non-zero THEN
    *       the stencil fail operator is to be applied
    *   ELSE
    *       the stencil fail operator is not to be applied
    *   ENDIF
    */
   switch (ctx->Stencil.Function[face]) {
      case GL_NEVER:
         /* never pass; always fail */
         for (i=0;i<n;i++) {
	    if (mask[i]) {
	       mask[i] = 0;
	       fail[i] = 1;
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 allfail = GL_TRUE;
	 break;
      case GL_LESS:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
	       s = (GLstencil) (stencil[i] & valueMask);
	       if (r < s) {
		  /* passed */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_LEQUAL:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
	       s = (GLstencil) (stencil[i] & valueMask);
	       if (r <= s) {
		  /* pass */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_GREATER:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
	       s = (GLstencil) (stencil[i] & valueMask);
	       if (r > s) {
		  /* passed */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_GEQUAL:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
	       s = (GLstencil) (stencil[i] & valueMask);
	       if (r >= s) {
		  /* passed */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_EQUAL:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
	       s = (GLstencil) (stencil[i] & valueMask);
	       if (r == s) {
		  /* passed */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_NOTEQUAL:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
	       s = (GLstencil) (stencil[i] & valueMask);
	       if (r != s) {
		  /* passed */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_ALWAYS:
	 /* always pass */
	 for (i=0;i<n;i++) {
	    fail[i] = 0;
	 }
	 break;
      default:
         _mesa_problem(ctx, "Bad stencil func in gl_stencil_span");
         return 0;
   }

   if (ctx->Stencil.FailFunc[face] != GL_KEEP) {
      apply_stencil_op( ctx, ctx->Stencil.FailFunc[face], face, n, stencil, fail );
   }

   return !allfail;
}


/**
 * Compute the zpass/zfail masks by comparing the pre- and post-depth test
 * masks.
 */
static INLINE void
compute_pass_fail_masks(GLuint n, const GLubyte origMask[],
                        const GLubyte newMask[],
                        GLubyte passMask[], GLubyte failMask[])
{
   GLuint i;
   for (i = 0; i < n; i++) {
      ASSERT(newMask[i] == 0 || newMask[i] == 1);
      passMask[i] = origMask[i] & newMask[i];
      failMask[i] = origMask[i] & (newMask[i] ^ 1);
   }
}


/**
 * Apply stencil and depth testing to the span of pixels.
 * Both software and hardware stencil buffers are acceptable.
 * Input:  n - number of pixels in the span
 *         x, y - location of leftmost pixel in span