draw_pipe_clip.c

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/**************************************************************************
 * 
 * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
 * 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, sub license, 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 (including the
 * next paragraph) 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 NON-INFRINGEMENT.
 * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS 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 "util/u_memory.h"
#include "util/u_math.h"

#include "pipe/p_shader_tokens.h"

#include "draw_vs.h"
#include "draw_pipe.h"


#ifndef IS_NEGATIVE
#define IS_NEGATIVE(X) ((X) < 0.0)
#endif

#ifndef DIFFERENT_SIGNS
#define DIFFERENT_SIGNS(x, y) ((x) * (y) <= 0.0F && (x) - (y) != 0.0F)
#endif

#ifndef MAX_CLIPPED_VERTICES
#define MAX_CLIPPED_VERTICES ((2 * (6 + PIPE_MAX_CLIP_PLANES))+1)
#endif



struct clipper {
   struct draw_stage stage;      
   /* Basically duplicate some of the flatshading logic here:
    */
   boolean flat;
   uint num_color_attribs;
   uint color_attribs[4];  /* front/back primary/secondary colors */

   float (*plane)[4];
};


/* This is a bit confusing:
 */
static INLINE struct clipper *clipper_stage( struct draw_stage *stage )
{
   return (struct clipper *)stage;
}


#define LINTERP(T, OUT, IN) ((OUT) + (T) * ((IN) - (OUT)))


/* All attributes are float[4], so this is easy:
 */
static void interp_attr( float *fdst,
                         float t,
                         const float *fin,
                         const float *fout )
{  
   fdst[0] = LINTERP( t, fout[0], fin[0] );
   fdst[1] = LINTERP( t, fout[1], fin[1] );
   fdst[2] = LINTERP( t, fout[2], fin[2] );
   fdst[3] = LINTERP( t, fout[3], fin[3] );
}

static void copy_colors( struct draw_stage *stage,
                         struct vertex_header *dst,
                         const struct vertex_header *src )
{
   const struct clipper *clipper = clipper_stage(stage);
   uint i;
   for (i = 0; i < clipper->num_color_attribs; i++) {
      const uint attr = clipper->color_attribs[i];
      COPY_4FV(dst->data[attr], src->data[attr]);
   }
}



/* Interpolate between two vertices to produce a third.  
 */
static void interp( const struct clipper *clip,
                    struct vertex_header *dst,
                    float t,
                    const struct vertex_header *out, 
                    const struct vertex_header *in )
{
   const unsigned nr_attrs = clip->stage.draw->vs.num_vs_outputs;
   const unsigned pos_attr = clip->stage.draw->vs.position_output;
   unsigned j;

   /* Vertex header.
    */
   {
      dst->clipmask = 0;
      dst->edgeflag = 0;        /* will get overwritten later */
      dst->pad = 0;
      dst->vertex_id = UNDEFINED_VERTEX_ID;
   }

   /* Clip coordinates:  interpolate normally
    */
   {
      interp_attr(dst->clip, t, in->clip, out->clip);
   }

   /* Do the projective divide and insert window coordinates:
    */
   {
      const float *pos = dst->clip;
      const float *scale = clip->stage.draw->viewport.scale;
      const float *trans = clip->stage.draw->viewport.translate;
      const float oow = 1.0f / pos[3];

      dst->data[pos_attr][0] = pos[0] * oow * scale[0] + trans[0];
      dst->data[pos_attr][1] = pos[1] * oow * scale[1] + trans[1];
      dst->data[pos_attr][2] = pos[2] * oow * scale[2] + trans[2];
      dst->data[pos_attr][3] = oow;
   }

   /* Other attributes
    */
   for (j = 0; j < nr_attrs; j++) {
      if (j != pos_attr)
         interp_attr(dst->data[j], t, in->data[j], out->data[j]);
   }
}


static void emit_poly( struct draw_stage *stage,
                       struct vertex_header **inlist,
                       unsigned n,
                       const struct prim_header *origPrim)
{
   struct prim_header header;
   unsigned i;

   const ushort edge_first  = DRAW_PIPE_EDGE_FLAG_2;
   const ushort edge_middle = DRAW_PIPE_EDGE_FLAG_0;
   const ushort edge_last   = DRAW_PIPE_EDGE_FLAG_1;

   /* later stages may need the determinant, but only the sign matters */
   header.det = origPrim->det;
   header.flags = DRAW_PIPE_RESET_STIPPLE | edge_first | edge_middle;
   header.pad = 0;

   for (i = 2; i < n; i++, header.flags = edge_middle) {
      header.v[0] = inlist[i-1];
      header.v[1] = inlist[i];
      header.v[2] = inlist[0];  /* keep in v[2] for flatshading */

      if (i == n-1)
        header.flags |= edge_last;

      if (0) {
         const struct draw_vertex_shader *vs = stage->draw->vs.vertex_shader;
         uint j, k;
         debug_printf("Clipped tri:\n");
         for (j = 0; j < 3; j++) {
            for (k = 0; k < vs->info.num_outputs; k++) {
               debug_printf("  Vert %d: Attr %d:  %f %f %f %f\n", j, k,
                            header.v[j]->data[k][0],
                            header.v[j]->data[k][1],
                            header.v[j]->data[k][2],
                            header.v[j]->data[k][3]);
            }
         }
      }

      stage->next->tri( stage->next, &header );
   }
}

static INLINE float
dot4(const float *a, const float *b)
{
   return (a[0]*b[0] +
           a[1]*b[1] +
           a[2]*b[2] +
           a[3]*b[3]);
}


/* Clip a triangle against the viewport and user clip planes.
 */
static void
do_clip_tri( struct draw_stage *stage, 
             struct prim_header *header,
             unsigned clipmask )
{
   struct clipper *clipper = clipper_stage( stage );
   struct vertex_header *a[MAX_CLIPPED_VERTICES];
   struct vertex_header *b[MAX_CLIPPED_VERTICES];
   struct vertex_header **inlist = a;
   struct vertex_header **outlist = b;
   unsigned tmpnr = 0;
   unsigned n = 3;
   unsigned i;

   inlist[0] = header->v[0];
   inlist[1] = header->v[1];
   inlist[2] = header->v[2];

   while (clipmask && n >= 3) {
      const unsigned plane_idx = ffs(clipmask)-1;
      const float *plane = clipper->plane[plane_idx];
      struct vertex_header *vert_prev = inlist[0];
      float dp_prev = dot4( vert_prev->clip, plane );
      unsigned outcount = 0;

      clipmask &= ~(1<<plane_idx);

      inlist[n] = inlist[0]; /* prevent rotation of vertices */

      for (i = 1; i <= n; i++) {
         struct vertex_header *vert = inlist[i];

         float dp = dot4( vert->clip, plane );

         if (!IS_NEGATIVE(dp_prev)) {
            outlist[outcount++] = vert_prev;
         }

         if (DIFFERENT_SIGNS(dp, dp_prev)) {
            struct vertex_header *new_vert = clipper->stage.tmp[tmpnr++];
            outlist[outcount++] = new_vert;

            if (IS_NEGATIVE(dp)) {
               /* Going out of bounds.  Avoid division by zero as we
                * know dp != dp_prev from DIFFERENT_SIGNS, above.
                */
               float t = dp / (dp - dp_prev);
               interp( clipper, new_vert, t, vert, vert_prev );
               
               /* Force edgeflag true in this case:
                */
               new_vert->edgeflag = 1;
            } else {
               /* Coming back in.
                */
               float t = dp_prev / (dp_prev - dp);
               interp( clipper, new_vert, t, vert_prev, vert );

               /* Copy starting vert's edgeflag:
                */
               new_vert->edgeflag = vert_prev->edgeflag;
            }
         }

         vert_prev = vert;
         dp_prev = dp;
      }

      {
         struct vertex_header **tmp = inlist;
         inlist = outlist;
         outlist = tmp;
         n = outcount;
      }
   }

   /* If flat-shading, copy color to new provoking vertex.
    */
   if (clipper->flat && inlist[0] != header->v[2]) {
      if (1) {
         inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
      }

      copy_colors(stage, inlist[0], header->v[2]);
   }



   /* Emit the polygon as triangles to the setup stage:
    */
   if (n >= 3)
      emit_poly( stage, inlist, n, header );
}


/* Clip a line against the viewport and user clip planes.
 */
static void
do_clip_line( struct draw_stage *stage,
              struct prim_header *header,
              unsigned clipmask )
{
   const struct clipper *clipper = clipper_stage( stage );
   struct vertex_header *v0 = header->v[0];
   struct vertex_header *v1 = header->v[1];
   const float *pos0 = v0->clip;
   const float *pos1 = v1->clip;
   float t0 = 0.0F;
   float t1 = 0.0F;
   struct prim_header newprim;

   while (clipmask) {
      const unsigned plane_idx = ffs(clipmask)-1;
      const float *plane = clipper->plane[plane_idx];
      const float dp0 = dot4( pos0, plane );
      const float dp1 = dot4( pos1, plane );

      if (dp1 < 0.0F) {
         float t = dp1 / (dp1 - dp0);
         t1 = MAX2(t1, t);
      } 

      if (dp0 < 0.0F) {
         float t = dp0 / (dp0 - dp1);
         t0 = MAX2(t0, t);
      }

      if (t0 + t1 >= 1.0F)
         return; /* discard */

      clipmask &= ~(1 << plane_idx);  /* turn off this plane's bit */
   }

   if (v0->clipmask) {
      interp( clipper, stage->tmp[0], t0, v0, v1 );

      if (clipper->flat)
         copy_colors(stage, stage->tmp[0], v0);

      newprim.v[0] = stage->tmp[0];
   }
   else {
      newprim.v[0] = v0;
   }

   if (v1->clipmask) {
      interp( clipper, stage->tmp[1], t1, v1, v0 );
      newprim.v[1] = stage->tmp[1];
   }
   else {
      newprim.v[1] = v1;
   }

   stage->next->line( stage->next, &newprim );
}


static void
clip_point( struct draw_stage *stage, 
            struct prim_header *header )
{
   if (header->v[0]->clipmask == 0) 
      stage->next->point( stage->next, header );
}


static void
clip_line( struct draw_stage *stage,
           struct prim_header *header )
{
   unsigned clipmask = (header->v[0]->clipmask | 
                        header->v[1]->clipmask);
   
   if (clipmask == 0) {
      /* no clipping needed */
      stage->next->line( stage->next, header );
   }
   else if ((header->v[0]->clipmask &
             header->v[1]->clipmask) == 0) {
      do_clip_line(stage, header, clipmask);
   }
   /* else, totally clipped */
}


static void
clip_tri( struct draw_stage *stage,
          struct prim_header *header )
{
   unsigned clipmask = (header->v[0]->clipmask | 
                        header->v[1]->clipmask | 
                        header->v[2]->clipmask);
   
   if (clipmask == 0) {
      /* no clipping needed */
      stage->next->tri( stage->next, header );
   }
   else if ((header->v[0]->clipmask & 
             header->v[1]->clipmask & 
             header->v[2]->clipmask) == 0) {
      do_clip_tri(stage, header, clipmask);
   }
}

/* Update state.  Could further delay this until we hit the first
 * primitive that really requires clipping.
 */
static void 
clip_init_state( struct draw_stage *stage )
{
   struct clipper *clipper = clipper_stage( stage );

   clipper->flat = stage->draw->rasterizer->flatshade ? TRUE : FALSE;

   if (clipper->flat) {
      const struct draw_vertex_shader *vs = stage->draw->vs.vertex_shader;
      uint i;

      clipper->num_color_attribs = 0;
      for (i = 0; i < vs->info.num_outputs; i++) {
         if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR ||
             vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
            clipper->color_attribs[clipper->num_color_attribs++] = i;
         }
      }
   }
   
   stage->tri = clip_tri;
   stage->line = clip_line;
}



static void clip_first_tri( struct draw_stage *stage,
                            struct prim_header *header )
{
   clip_init_state( stage );
   stage->tri( stage, header );
}

static void clip_first_line( struct draw_stage *stage,
                             struct prim_header *header )
{
   clip_init_state( stage );
   stage->line( stage, header );
}


static void clip_flush( struct draw_stage *stage, 
                             unsigned flags )
{
   stage->tri = clip_first_tri;
   stage->line = clip_first_line;
   stage->next->flush( stage->next, flags );
}


static void clip_reset_stipple_counter( struct draw_stage *stage )
{
   stage->next->reset_stipple_counter( stage->next );
}


static void clip_destroy( struct draw_stage *stage )
{
   draw_free_temp_verts( stage );
   FREE( stage );
}


struct draw_stage *draw_clip_stage( struct draw_context *draw )
{
   struct clipper *clipper = CALLOC_STRUCT(clipper);
   if (clipper == NULL)
      goto fail;

   if (!draw_alloc_temp_verts( &clipper->stage, MAX_CLIPPED_VERTICES+1 ))
      goto fail;

   clipper->stage.draw = draw;
   clipper->stage.point = clip_point;
   clipper->stage.line = clip_first_line;
   clipper->stage.tri = clip_first_tri;
   clipper->stage.flush = clip_flush;
   clipper->stage.reset_stipple_counter = clip_reset_stipple_counter;
   clipper->stage.destroy = clip_destroy;

   clipper->plane = draw->plane;

   return &clipper->stage;

 fail:
   if (clipper)
      clipper->stage.destroy( &clipper->stage );

   return NULL;
}

---