/************************************************************************** * * 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. * **************************************************************************/ /** * \brief Clipping stage * * \author Keith Whitwell */ #include "util/u_memory.h" #include "util/u_math.h" #include "pipe/p_shader_tokens.h" #include "draw_vs.h" #include "draw_pipe.h" #include "draw_fs.h" #include "draw_gs.h" /** Set to 1 to enable printing of coords before/after clipping */ #define DEBUG_CLIP 0 #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 #define MAX_CLIPPED_VERTICES ((2 * (6 + PIPE_MAX_CLIP_PLANES))+1) struct clip_stage { struct draw_stage stage; /**< base class */ /* List of the attributes to be flatshaded. */ uint num_flat_attribs; uint flat_attribs[PIPE_MAX_SHADER_OUTPUTS]; /* Mask of attributes in noperspective mode */ boolean noperspective_attribs[PIPE_MAX_SHADER_OUTPUTS]; float (*plane)[4]; }; /** Cast wrapper */ static INLINE struct clip_stage *clip_stage( struct draw_stage *stage ) { return (struct clip_stage *)stage; } static INLINE unsigned draw_viewport_index(struct draw_context *draw, const struct vertex_header *leading_vertex) { if (draw_current_shader_uses_viewport_index(draw)) { unsigned viewport_index_output = draw_current_shader_viewport_index_output(draw); unsigned viewport_index = *((unsigned*)leading_vertex->data[viewport_index_output]); return draw_clamp_viewport_idx(viewport_index); } else { return 0; } } #define LINTERP(T, OUT, IN) ((OUT) + (T) * ((IN) - (OUT))) /* All attributes are float[4], so this is easy: */ static void interp_attr( float dst[4], float t, const float in[4], const float out[4] ) { dst[0] = LINTERP( t, out[0], in[0] ); dst[1] = LINTERP( t, out[1], in[1] ); dst[2] = LINTERP( t, out[2], in[2] ); dst[3] = LINTERP( t, out[3], in[3] ); } /** * Copy flat shaded attributes src vertex to dst vertex. */ static void copy_flat( struct draw_stage *stage, struct vertex_header *dst, const struct vertex_header *src ) { const struct clip_stage *clipper = clip_stage(stage); uint i; for (i = 0; i < clipper->num_flat_attribs; i++) { const uint attr = clipper->flat_attribs[i]; COPY_4FV(dst->data[attr], src->data[attr]); } } /* Interpolate between two vertices to produce a third. */ static void interp( const struct clip_stage *clip, struct vertex_header *dst, float t, const struct vertex_header *out, const struct vertex_header *in, unsigned viewport_index ) { const unsigned nr_attrs = draw_num_shader_outputs(clip->stage.draw); const unsigned pos_attr = draw_current_shader_position_output(clip->stage.draw); const unsigned clip_attr = draw_current_shader_clipvertex_output(clip->stage.draw); unsigned j; float t_nopersp; /* Vertex header. */ dst->clipmask = 0; dst->edgeflag = 0; /* will get overwritten later */ dst->have_clipdist = in->have_clipdist; dst->vertex_id = UNDEFINED_VERTEX_ID; /* Interpolate the clip-space coords. */ interp_attr(dst->clip, t, in->clip, out->clip); /* interpolate the clip-space position */ interp_attr(dst->pre_clip_pos, t, in->pre_clip_pos, out->pre_clip_pos); /* Do the projective divide and viewport transformation to get * new window coordinates: */ { const float *pos = dst->pre_clip_pos; const float *scale = clip->stage.draw->viewports[viewport_index].scale; const float *trans = clip->stage.draw->viewports[viewport_index].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; } /** * Compute the t in screen-space instead of 3d space to use * for noperspective interpolation. * * The points can be aligned with the X axis, so in that case try * the Y. When both points are at the same screen position, we can * pick whatever value (the interpolated point won't be in front * anyway), so just use the 3d t. */ { int k; t_nopersp = t; /* find either in.x != out.x or in.y != out.y */ for (k = 0; k < 2; k++) { if (in->clip[k] != out->clip[k]) { /* do divide by W, then compute linear interpolation factor */ float in_coord = in->clip[k] / in->clip[3]; float out_coord = out->clip[k] / out->clip[3]; float dst_coord = dst->clip[k] / dst->clip[3]; t_nopersp = (dst_coord - out_coord) / (in_coord - out_coord); break; } } } /* Other attributes */ for (j = 0; j < nr_attrs; j++) { if (j != pos_attr && j != clip_attr) { if (clip->noperspective_attribs[j]) interp_attr(dst->data[j], t_nopersp, in->data[j], out->data[j]); else interp_attr(dst->data[j], t, in->data[j], out->data[j]); } } } /** * Checks whether the specifed triangle is empty and if it is returns * true, otherwise returns false. * Triangle is considered null/empty if it's area is qual to zero. */ static INLINE boolean is_tri_null(struct draw_context *draw, const struct prim_header *header) { const unsigned pos_attr = draw_current_shader_position_output(draw); float x1 = header->v[1]->data[pos_attr][0] - header->v[0]->data[pos_attr][0]; float y1 = header->v[1]->data[pos_attr][1] - header->v[0]->data[pos_attr][1]; float z1 = header->v[1]->data[pos_attr][2] - header->v[0]->data[pos_attr][2]; float x2 = header->v[2]->data[pos_attr][0] - header->v[0]->data[pos_attr][0]; float y2 = header->v[2]->data[pos_attr][1] - header->v[0]->data[pos_attr][1]; float z2 = header->v[2]->data[pos_attr][2] - header->v[0]->data[pos_attr][2]; float vx = y1 * z2 - z1 * y2; float vy = x1 * z2 - z1 * x2; float vz = x1 * y2 - y1 * x2; return (vx*vx + vy*vy + vz*vz) == 0.f; } /** * Emit a post-clip polygon to the next pipeline stage. The polygon * will be convex and the provoking vertex will always be vertex[0]. */ static void emit_poly( struct draw_stage *stage, struct vertex_header **inlist, const boolean *edgeflags, unsigned n, const struct prim_header *origPrim) { struct prim_header header; unsigned i; ushort edge_first, edge_middle, edge_last; boolean last_tri_was_null = FALSE; boolean tri_was_not_null = FALSE; if (stage->draw->rasterizer->flatshade_first) { edge_first = DRAW_PIPE_EDGE_FLAG_0; edge_middle = DRAW_PIPE_EDGE_FLAG_1; edge_last = DRAW_PIPE_EDGE_FLAG_2; } else { edge_first = DRAW_PIPE_EDGE_FLAG_2; edge_middle = DRAW_PIPE_EDGE_FLAG_0; edge_last = DRAW_PIPE_EDGE_FLAG_1; } if (!edgeflags[0]) edge_first = 0; /* 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) { boolean tri_null; /* order the triangle verts to respect the provoking vertex mode */ if (stage->draw->rasterizer->flatshade_first) { header.v[0] = inlist[0]; /* the provoking vertex */ header.v[1] = inlist[i-1]; header.v[2] = inlist[i]; } else { header.v[0] = inlist[i-1]; header.v[1] = inlist[i]; header.v[2] = inlist[0]; /* the provoking vertex */ } tri_null = is_tri_null(stage->draw, &header); /* If we generated a triangle with an area, aka. non-null triangle, * or if the previous triangle was also null then skip all subsequent * null triangles */ if ((tri_was_not_null && tri_null) || (last_tri_was_null && tri_null)) { last_tri_was_null = tri_null; continue; } last_tri_was_null = tri_null; if (!tri_null) { tri_was_not_null = TRUE; } if (!edgeflags[i-1]) { header.flags &= ~edge_middle; } if (i == n - 1 && edgeflags[i]) header.flags |= edge_last; if (DEBUG_CLIP) { uint j, k; debug_printf("Clipped tri: (flat-shade-first = %d)\n", stage->draw->rasterizer->flatshade_first); for (j = 0; j < 3; j++) { debug_printf(" Vert %d: clip: %f %f %f %f\n", j, header.v[j]->clip[0], header.v[j]->clip[1], header.v[j]->clip[2], header.v[j]->clip[3]); for (k = 0; k < draw_num_shader_outputs(stage->draw); 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]); } /* * this function extracts the clip distance for the current plane, * it first checks if the shader provided a clip distance, otherwise * it works out the value using the clipvertex */ static INLINE float getclipdist(const struct clip_stage *clipper, struct vertex_header *vert, int plane_idx) { const float *plane; float dp; if (vert->have_clipdist && plane_idx >= 6) { /* pick the correct clipdistance element from the output vectors */ int _idx = plane_idx - 6; int cdi = _idx >= 4; int vidx = cdi ? _idx - 4 : _idx; dp = vert->data[draw_current_shader_clipdistance_output(clipper->stage.draw, cdi)][vidx]; } else { plane = clipper->plane[plane_idx]; dp = dot4(vert->clip, plane); } return dp; } /* 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 clip_stage *clipper = clip_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; boolean aEdges[MAX_CLIPPED_VERTICES]; boolean bEdges[MAX_CLIPPED_VERTICES]; boolean *inEdges = aEdges; boolean *outEdges = bEdges; int viewport_index = 0; inlist[0] = header->v[0]; inlist[1] = header->v[1]; inlist[2] = header->v[2]; viewport_index = draw_viewport_index(clipper->stage.draw, inlist[0]); if (DEBUG_CLIP) { const float *v0 = header->v[0]->clip; const float *v1 = header->v[1]->clip; const float *v2 = header->v[2]->clip; debug_printf("Clip triangle:\n"); debug_printf(" %f, %f, %f, %f\n", v0[0], v0[1], v0[2], v0[3]); debug_printf(" %f, %f, %f, %f\n", v1[0], v1[1], v1[2], v1[3]); debug_printf(" %f, %f, %f, %f\n", v2[0], v2[1], v2[2], v2[3]); } /* * Note: at this point we can't just use the per-vertex edge flags. * We have to observe the edge flag bits set in header->flags which * were set during primitive decomposition. Put those flags into * an edge flags array which parallels the vertex array. * Later, in the 'unfilled' pipeline stage we'll draw the edge if both * the header.flags bit is set AND the per-vertex edgeflag field is set. */ inEdges[0] = !!(header->flags & DRAW_PIPE_EDGE_FLAG_0); inEdges[1] = !!(header->flags & DRAW_PIPE_EDGE_FLAG_1); inEdges[2] = !!(header->flags & DRAW_PIPE_EDGE_FLAG_2); while (clipmask && n >= 3) { const unsigned plane_idx = ffs(clipmask)-1; const boolean is_user_clip_plane = plane_idx >= 6; struct vertex_header *vert_prev = inlist[0]; boolean *edge_prev = &inEdges[0]; float dp_prev; unsigned outcount = 0; dp_prev = getclipdist(clipper, vert_prev, plane_idx); clipmask &= ~(1<= MAX_CLIPPED_VERTICES) return; inlist[n] = inlist[0]; /* prevent rotation of vertices */ inEdges[n] = inEdges[0]; for (i = 1; i <= n; i++) { struct vertex_header *vert = inlist[i]; boolean *edge = &inEdges[i]; float dp = getclipdist(clipper, vert, plane_idx); if (util_is_inf_or_nan(dp)) return; //discard nan if (!IS_NEGATIVE(dp_prev)) { assert(outcount < MAX_CLIPPED_VERTICES); if (outcount >= MAX_CLIPPED_VERTICES) return; outEdges[outcount] = *edge_prev; outlist[outcount++] = vert_prev; } if (DIFFERENT_SIGNS(dp, dp_prev)) { struct vertex_header *new_vert; boolean *new_edge; assert(tmpnr < MAX_CLIPPED_VERTICES + 1); if (tmpnr >= MAX_CLIPPED_VERTICES + 1) return; new_vert = clipper->stage.tmp[tmpnr++]; assert(outcount < MAX_CLIPPED_VERTICES); if (outcount >= MAX_CLIPPED_VERTICES) return; new_edge = &outEdges[outcount]; 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, viewport_index ); /* Whether or not to set edge flag for the new vert depends * on whether it's a user-defined clipping plane. We're * copying NVIDIA's behaviour here. */ if (is_user_clip_plane) { /* we want to see an edge along the clip plane */ *new_edge = TRUE; new_vert->edgeflag = TRUE; } else { /* we don't want to see an edge along the frustum clip plane */ *new_edge = *edge_prev; new_vert->edgeflag = FALSE; } } else { /* Coming back in. */ float t = dp_prev / (dp_prev - dp); interp( clipper, new_vert, t, vert_prev, vert, viewport_index ); /* Copy starting vert's edgeflag: */ new_vert->edgeflag = vert_prev->edgeflag; *new_edge = *edge_prev; } } vert_prev = vert; edge_prev = edge; dp_prev = dp; } /* swap in/out lists */ { struct vertex_header **tmp = inlist; inlist = outlist; outlist = tmp; n = outcount; } { boolean *tmp = inEdges; inEdges = outEdges; outEdges = tmp; } } /* If flat-shading, copy provoking vertex color to polygon vertex[0] */ if (n >= 3) { if (clipper->num_flat_attribs) { if (stage->draw->rasterizer->flatshade_first) { if (inlist[0] != header->v[0]) { assert(tmpnr < MAX_CLIPPED_VERTICES + 1); if (tmpnr >= MAX_CLIPPED_VERTICES + 1) return; inlist[0] = dup_vert(stage, inlist[0], tmpnr++); copy_flat(stage, inlist[0], header->v[0]); } } else { if (inlist[0] != header->v[2]) { assert(tmpnr < MAX_CLIPPED_VERTICES + 1); if (tmpnr >= MAX_CLIPPED_VERTICES + 1) return; inlist[0] = dup_vert(stage, inlist[0], tmpnr++); copy_flat(stage, inlist[0], header->v[2]); } } } /* Emit the polygon as triangles to the setup stage: */ emit_poly( stage, inlist, inEdges, 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 clip_stage *clipper = clip_stage( stage ); struct vertex_header *v0 = header->v[0]; struct vertex_header *v1 = header->v[1]; float t0 = 0.0F; float t1 = 0.0F; struct prim_header newprim; int viewport_index = draw_viewport_index(clipper->stage.draw, v0); while (clipmask) { const unsigned plane_idx = ffs(clipmask)-1; const float dp0 = getclipdist(clipper, v0, plane_idx); const float dp1 = getclipdist(clipper, v1, plane_idx); if (util_is_inf_or_nan(dp0) || util_is_inf_or_nan(dp1)) return; //discard nan 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, viewport_index ); if (stage->draw->rasterizer->flatshade_first) { copy_flat(stage, stage->tmp[0], v0); /* copy v0 color to tmp[0] */ } else { copy_flat(stage, stage->tmp[0], v1); /* copy v1 color to tmp[0] */ } newprim.v[0] = stage->tmp[0]; } else { newprim.v[0] = v0; } if (v1->clipmask) { interp( clipper, stage->tmp[1], t1, v1, v0, viewport_index ); if (stage->draw->rasterizer->flatshade_first) { copy_flat(stage, stage->tmp[1], v0); /* copy v0 color to tmp[1] */ } else { copy_flat(stage, stage->tmp[1], v1); /* copy v1 color to tmp[1] */ } 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); } } static int find_interp(const struct draw_fragment_shader *fs, int *indexed_interp, uint semantic_name, uint semantic_index) { int interp; /* If it's gl_{Front,Back}{,Secondary}Color, pick up the mode * from the array we've filled before. */ if (semantic_name == TGSI_SEMANTIC_COLOR || semantic_name == TGSI_SEMANTIC_BCOLOR) { interp = indexed_interp[semantic_index]; } else { /* Otherwise, search in the FS inputs, with a decent default * if we don't find it. */ uint j; interp = TGSI_INTERPOLATE_PERSPECTIVE; if (fs) { for (j = 0; j < fs->info.num_inputs; j++) { if (semantic_name == fs->info.input_semantic_name[j] && semantic_index == fs->info.input_semantic_index[j]) { interp = fs->info.input_interpolate[j]; break; } } } } return interp; } /* 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 clip_stage *clipper = clip_stage( stage ); const struct draw_fragment_shader *fs = stage->draw->fs.fragment_shader; uint i, j; const struct tgsi_shader_info *info = draw_get_shader_info(stage->draw); /* We need to know for each attribute what kind of interpolation is * done on it (flat, smooth or noperspective). But the information * is not directly accessible for outputs, only for inputs. So we * have to match semantic name and index between the VS (or GS/ES) * outputs and the FS inputs to get to the interpolation mode. * * The only hitch is with gl_FrontColor/gl_BackColor which map to * gl_Color, and their Secondary versions. First there are (up to) * two outputs for one input, so we tuck the information in a * specific array. Second if they don't have qualifiers, the * default value has to be picked from the global shade mode. * * Of course, if we don't have a fragment shader in the first * place, defaults should be used. */ /* First pick up the interpolation mode for * gl_Color/gl_SecondaryColor, with the correct default. */ int indexed_interp[2]; indexed_interp[0] = indexed_interp[1] = stage->draw->rasterizer->flatshade ? TGSI_INTERPOLATE_CONSTANT : TGSI_INTERPOLATE_PERSPECTIVE; if (fs) { for (i = 0; i < fs->info.num_inputs; i++) { if (fs->info.input_semantic_name[i] == TGSI_SEMANTIC_COLOR) { if (fs->info.input_interpolate[i] != TGSI_INTERPOLATE_COLOR) indexed_interp[fs->info.input_semantic_index[i]] = fs->info.input_interpolate[i]; } } } /* Then resolve the interpolation mode for every output attribute. * * Given how the rest of the code, the most efficient way is to * have a vector of flat-mode attributes, and a mask for * noperspective attributes. */ clipper->num_flat_attribs = 0; memset(clipper->noperspective_attribs, 0, sizeof(clipper->noperspective_attribs)); for (i = 0; i < info->num_outputs; i++) { /* Find the interpolation mode for a specific attribute */ int interp = find_interp(fs, indexed_interp, info->output_semantic_name[i], info->output_semantic_index[i]); /* If it's flat, add it to the flat vector. Otherwise update * the noperspective mask. */ if (interp == TGSI_INTERPOLATE_CONSTANT) { clipper->flat_attribs[clipper->num_flat_attribs] = i; clipper->num_flat_attribs++; } else clipper->noperspective_attribs[i] = interp == TGSI_INTERPOLATE_LINEAR; } /* Search the extra vertex attributes */ for (j = 0; j < stage->draw->extra_shader_outputs.num; j++) { /* Find the interpolation mode for a specific attribute */ int interp = find_interp(fs, indexed_interp, stage->draw->extra_shader_outputs.semantic_name[j], stage->draw->extra_shader_outputs.semantic_index[j]); /* If it's flat, add it to the flat vector. Otherwise update * the noperspective mask. */ if (interp == TGSI_INTERPOLATE_CONSTANT) { clipper->flat_attribs[clipper->num_flat_attribs] = i + j; clipper->num_flat_attribs++; } else clipper->noperspective_attribs[i + j] = interp == TGSI_INTERPOLATE_LINEAR; } 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 ); } /** * Allocate a new clipper stage. * \return pointer to new stage object */ struct draw_stage *draw_clip_stage( struct draw_context *draw ) { struct clip_stage *clipper = CALLOC_STRUCT(clip_stage); if (clipper == NULL) goto fail; clipper->stage.draw = draw; clipper->stage.name = "clipper"; 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; if (!draw_alloc_temp_verts( &clipper->stage, MAX_CLIPPED_VERTICES+1 )) goto fail; return &clipper->stage; fail: if (clipper) clipper->stage.destroy( &clipper->stage ); return NULL; }