s_stencil.c

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

 *         z - array [n] of z values
 *         mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
 * Output:  mask - array [n] of flags (1=stencil and depth test passed)
 * Return: GL_FALSE - all fragments failed the testing
 *         GL_TRUE - one or more fragments passed the testing
 *
 */
static GLboolean
stencil_and_ztest_span(GLcontext *ctx, SWspan *span, GLuint face)
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_StencilBuffer;
   GLstencil stencilRow[MAX_WIDTH];
   GLstencil *stencil;
   const GLuint n = span->end;
   const GLint x = span->x;
   const GLint y = span->y;
   GLubyte *mask = span->array->mask;

   ASSERT((span->arrayMask & SPAN_XY) == 0);
   ASSERT(ctx->Stencil.Enabled);
   ASSERT(n <= MAX_WIDTH);
#ifdef DEBUG
   if (ctx->Depth.Test) {
      ASSERT(span->arrayMask & SPAN_Z);
   }
#endif

   stencil = (GLstencil *) rb->GetPointer(ctx, rb, x, y);
   if (!stencil) {
      rb->GetRow(ctx, rb, n, x, y, stencilRow);
      stencil = stencilRow;
   }

   /*
    * Apply the stencil test to the fragments.
    * failMask[i] is 1 if the stencil test failed.
    */
   if (do_stencil_test( ctx, face, n, stencil, mask ) == GL_FALSE) {
      /* all fragments failed the stencil test, we're done. */
      span->writeAll = GL_FALSE;
      if (!rb->GetPointer(ctx, rb, 0, 0)) {
         /* put updated stencil values into buffer */
         rb->PutRow(ctx, rb, n, x, y, stencil, NULL);
      }
      return GL_FALSE;
   }

   /*
    * Some fragments passed the stencil test, apply depth test to them
    * and apply Zpass and Zfail stencil ops.
    */
   if (ctx->Depth.Test == GL_FALSE) {
      /*
       * No depth buffer, just apply zpass stencil function to active pixels.
       */
      apply_stencil_op( ctx, ctx->Stencil.ZPassFunc[face], face, n, stencil, mask );
   }
   else {
      /*
       * Perform depth buffering, then apply zpass or zfail stencil function.
       */
      GLubyte passMask[MAX_WIDTH], failMask[MAX_WIDTH], origMask[MAX_WIDTH];

      /* save the current mask bits */
      _mesa_memcpy(origMask, mask, n * sizeof(GLubyte));

      /* apply the depth test */
      _swrast_depth_test_span(ctx, span);

      compute_pass_fail_masks(n, origMask, mask, passMask, failMask);

      /* apply the pass and fail operations */
      if (ctx->Stencil.ZFailFunc[face] != GL_KEEP) {
         apply_stencil_op( ctx, ctx->Stencil.ZFailFunc[face], face,
                           n, stencil, failMask );
      }
      if (ctx->Stencil.ZPassFunc[face] != GL_KEEP) {
         apply_stencil_op( ctx, ctx->Stencil.ZPassFunc[face], face,
                           n, stencil, passMask );
      }
   }

   /*
    * Write updated stencil values back into hardware stencil buffer.
    */
   if (!rb->GetPointer(ctx, rb, 0, 0)) {
      rb->PutRow(ctx, rb, n, x, y, stencil, NULL);
   }
   
   span->writeAll = GL_FALSE;
   
   return GL_TRUE;  /* one or more fragments passed both tests */
}



/*
 * Return the address of a stencil buffer value given the window coords:
 */
#define STENCIL_ADDRESS(X, Y)  (stencilStart + (Y) * stride + (X))



/**
 * Apply the given stencil operator for each pixel in the array whose
 * mask flag is set.
 * \note  This is for software stencil buffers only.
 * Input:  n - number of pixels in the span
 *         x, y - array of [n] pixels
 *         operator - the stencil buffer operator
 *         mask - array [n] of flag:  1=apply operator, 0=don't apply operator
 */
static void
apply_stencil_op_to_pixels( GLcontext *ctx,
                            GLuint n, const GLint x[], const GLint y[],
                            GLenum oper, GLuint face, const GLubyte mask[] )
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_StencilBuffer;
   const GLstencil stencilMax = (1 << fb->Visual.stencilBits) - 1;
   const GLstencil ref = ctx->Stencil.Ref[face];
   const GLstencil wrtmask = ctx->Stencil.WriteMask[face];
   const GLstencil invmask = (GLstencil) (~wrtmask);
   GLuint i;
   GLstencil *stencilStart = (GLubyte *) rb->Data;
   const GLuint stride = rb->Width;

   ASSERT(rb->GetPointer(ctx, rb, 0, 0));
   ASSERT(sizeof(GLstencil) == 1);

   switch (oper) {
      case GL_KEEP:
         /* do nothing */
         break;
      case GL_ZERO:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = 0;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
		  *sptr = (GLstencil) (invmask & *sptr);
	       }
	    }
	 }
	 break;
      case GL_REPLACE:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = ref;
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
		  *sptr = (GLstencil) ((invmask & *sptr ) | (wrtmask & ref));
	       }
	    }
	 }
	 break;
      case GL_INCR:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
		  if (*sptr < stencilMax) {
		     *sptr = (GLstencil) (*sptr + 1);
		  }
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
		  if (*sptr < stencilMax) {
		     *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr+1)));
		  }
	       }
	    }
	 }
	 break;
      case GL_DECR:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
		  if (*sptr>0) {
		     *sptr = (GLstencil) (*sptr - 1);
		  }
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
		  if (*sptr>0) {
		     *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr-1)));
		  }
	       }
	    }
	 }
	 break;
      case GL_INCR_WRAP_EXT:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = (GLstencil) (*sptr + 1);
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr+1)));
	       }
	    }
	 }
	 break;
      case GL_DECR_WRAP_EXT:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = (GLstencil) (*sptr - 1);
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr-1)));
	       }
	    }
	 }
	 break;
      case GL_INVERT:
	 if (invmask==0) {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = (GLstencil) (~*sptr);
	       }
	    }
	 }
	 else {
	    for (i=0;i<n;i++) {
	       if (mask[i]) {
                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                  *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & ~*sptr));
	       }
	    }
	 }
	 break;
      default:
         _mesa_problem(ctx, "Bad stencilop in apply_stencil_op_to_pixels");
   }
}



/**
 * Apply stencil test to an array of pixels before depth buffering.
 *
 * \note Used for software stencil buffer only.
 * Input:  n - number of pixels in the span
 *         x, y - array of [n] pixels to stencil
 *         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.
 * \return  GL_FALSE = all pixels failed, GL_TRUE = zero or more pixels passed.
 */
static GLboolean
stencil_test_pixels( GLcontext *ctx, GLuint face, GLuint n,
                     const GLint x[], const GLint y[], GLubyte mask[] )
{
   const struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_StencilBuffer;
   GLubyte fail[MAX_WIDTH];
   GLstencil r, s;
   GLuint i;
   GLboolean allfail = GL_FALSE;
   const GLuint valueMask = ctx->Stencil.ValueMask[face];
   const GLstencil *stencilStart = (GLstencil *) rb->Data;
   const GLuint stride = rb->Width;

   ASSERT(rb->GetPointer(ctx, rb, 0, 0));
   ASSERT(sizeof(GLstencil) == 1);

   /*
    * 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:
         /* 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]) {
               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
	       s = (GLstencil) (*sptr & 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]) {
               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
	       s = (GLstencil) (*sptr & 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]) {
               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
	       s = (GLstencil) (*sptr & 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]) {
               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
	       s = (GLstencil) (*sptr & 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]) {
               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
	       s = (GLstencil) (*sptr & valueMask);
	       if (r == s) {
		  /* passed */
		  fail[i] = 0;