auxiliary/draw/draw_pipe_wide_point.c

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/* Authors:  Keith Whitwell <keithw@vmware.com>
 */

/**
 * Notes on wide points and sprite mode:
 *
 * In wide point/sprite mode we effectively need to convert each incoming
 * vertex into four outgoing vertices specifying the corners of a quad.
 * Since we don't (yet) have geometry shaders, we have to handle this here
 * in the draw module.
 *
 * For sprites, it also means that this is where we have to handle texcoords
 * for the vertices of the quad.  OpenGL's GL_COORD_REPLACE state specifies
 * if/how enabled texcoords are automatically generated for sprites.  We pass
 * that info through gallium in the pipe_rasterizer_state::sprite_coord_mode
 * array.
 *
 * Additionally, GLSL's gl_PointCoord fragment attribute has to be handled
 * here as well.  This is basically an additional texture/generic attribute
 * that varies .x from 0 to 1 horizontally across the point and varies .y
 * vertically from 0 to 1 down the sprite.
 *
 * With geometry shaders, the gallium frontends could create a GS to do
 * most/all of this.
 */


#include "pipe/p_screen.h"
#include "pipe/p_context.h"
#include "util/u_math.h"
#include "util/u_memory.h"
#include "pipe/p_defines.h"
#include "pipe/p_shader_tokens.h"
#include "draw_fs.h"
#include "draw_vs.h"
#include "draw_pipe.h"


struct widepoint_stage {
   struct draw_stage stage;  /**< base class */

   float half_point_size;

   float xbias;
   float ybias;

   /** for automatic texcoord generation/replacement */
   uint num_texcoord_gen;
   uint texcoord_gen_slot[PIPE_MAX_SHADER_OUTPUTS];

   /* TGSI_SEMANTIC to which sprite_coord_enable applies */
   enum tgsi_semantic sprite_coord_semantic;

   int psize_slot;
};


static inline struct widepoint_stage *
widepoint_stage( struct draw_stage *stage )
{
   return (struct widepoint_stage *)stage;
}


/**
 * Set the vertex texcoords for sprite mode.
 * Coords may be left untouched or set to a right-side-up or upside-down
 * orientation.
 */
static void set_texcoords(const struct widepoint_stage *wide,
                          struct vertex_header *v, const float tc[4])
{
   const struct draw_context *draw = wide->stage.draw;
   const struct pipe_rasterizer_state *rast = draw->rasterizer;
   const uint texcoord_mode = rast->sprite_coord_mode;
   uint i;

   for (i = 0; i < wide->num_texcoord_gen; i++) {
      const uint slot = wide->texcoord_gen_slot[i];
      v->data[slot][0] = tc[0];
      if (texcoord_mode == PIPE_SPRITE_COORD_LOWER_LEFT)
         v->data[slot][1] = 1.0f - tc[1];
      else
         v->data[slot][1] = tc[1];
      v->data[slot][2] = tc[2];
      v->data[slot][3] = tc[3];
   }
}


/* If there are lots of sprite points (and why wouldn't there be?) it
 * would probably be more sensible to change hardware setup to
 * optimize this rather than doing the whole thing in software like
 * this.
 */
static void widepoint_point( struct draw_stage *stage,
                             struct prim_header *header )
{
   const struct widepoint_stage *wide = widepoint_stage(stage);
   const unsigned pos = draw_current_shader_position_output(stage->draw);
   const boolean sprite = (boolean) stage->draw->rasterizer->point_quad_rasterization;
   float half_size;
   float left_adj, right_adj, bot_adj, top_adj;

   struct prim_header tri;

   /* four dups of original vertex */
   struct vertex_header *v0 = dup_vert(stage, header->v[0], 0);
   struct vertex_header *v1 = dup_vert(stage, header->v[0], 1);
   struct vertex_header *v2 = dup_vert(stage, header->v[0], 2);
   struct vertex_header *v3 = dup_vert(stage, header->v[0], 3);

   float *pos0 = v0->data[pos];
   float *pos1 = v1->data[pos];
   float *pos2 = v2->data[pos];
   float *pos3 = v3->data[pos];

   /* point size is either per-vertex or fixed size */
   if (wide->psize_slot >= 0) {
      half_size = header->v[0]->data[wide->psize_slot][0];
      half_size *= 0.5f;
   }
   else {
      half_size = wide->half_point_size;
   }

   left_adj = -half_size + wide->xbias;
   right_adj = half_size + wide->xbias;
   bot_adj = half_size + wide->ybias;
   top_adj = -half_size + wide->ybias;

   pos0[0] += left_adj;
   pos0[1] += top_adj;

   pos1[0] += left_adj;
   pos1[1] += bot_adj;

   pos2[0] += right_adj;
   pos2[1] += top_adj;

   pos3[0] += right_adj;
   pos3[1] += bot_adj;

   if (sprite) {
      static const float tex00[4] = { 0, 0, 0, 1 };
      static const float tex01[4] = { 0, 1, 0, 1 };
      static const float tex11[4] = { 1, 1, 0, 1 };
      static const float tex10[4] = { 1, 0, 0, 1 };
      set_texcoords( wide, v0, tex00 );
      set_texcoords( wide, v1, tex01 );
      set_texcoords( wide, v2, tex10 );
      set_texcoords( wide, v3, tex11 );
   }

   tri.det = header->det;  /* only the sign matters */
   tri.v[0] = v0;
   tri.v[1] = v2;
   tri.v[2] = v3;
   stage->next->tri( stage->next, &tri );

   tri.v[0] = v0;
   tri.v[1] = v3;
   tri.v[2] = v1;
   stage->next->tri( stage->next, &tri );
}


static void
widepoint_first_point(struct draw_stage *stage,
                      struct prim_header *header)
{
   struct widepoint_stage *wide = widepoint_stage(stage);
   struct draw_context *draw = stage->draw;
   struct pipe_context *pipe = draw->pipe;
   const struct pipe_rasterizer_state *rast = draw->rasterizer;
   void *r;

   wide->half_point_size = 0.5f * rast->point_size;
   wide->xbias = 0.0;
   wide->ybias = 0.0;

   if (rast->half_pixel_center) {
      wide->xbias = 0.125;
      wide->ybias = -0.125;
   }

   /* Disable triangle culling, stippling, unfilled mode etc. */
   r = draw_get_rasterizer_no_cull(draw, rast);
   draw->suspend_flushing = TRUE;
   pipe->bind_rasterizer_state(pipe, r);
   draw->suspend_flushing = FALSE;

   /* XXX we won't know the real size if it's computed by the vertex shader! */
   if ((rast->point_size > draw->pipeline.wide_point_threshold) ||
       (rast->point_quad_rasterization && draw->pipeline.point_sprite)) {
      stage->point = widepoint_point;
   }
   else {
      stage->point = draw_pipe_passthrough_point;
   }

   draw_remove_extra_vertex_attribs(draw);

   if (rast->point_quad_rasterization) {
      const struct draw_fragment_shader *fs = draw->fs.fragment_shader;
      uint i;

      assert(fs);

      wide->num_texcoord_gen = 0;

      /* Loop over fragment shader inputs looking for the PCOORD input or inputs
       * for which bit 'k' in sprite_coord_enable is set.
       */
      for (i = 0; i < fs->info.num_inputs; i++) {
         int slot;
         const enum tgsi_semantic sn = fs->info.input_semantic_name[i];
         const unsigned si = fs->info.input_semantic_index[i];

         if (sn == wide->sprite_coord_semantic) {
            /* Note that sprite_coord_enable is a bitfield of 32 bits. */
            if (si >= 32 || !(rast->sprite_coord_enable & (1 << si)))
               continue;
         } else if (sn != TGSI_SEMANTIC_PCOORD) {
            continue;
         }

         /* OK, this generic attribute needs to be replaced with a
          * sprite coord (see above).
          */
         slot = draw_alloc_extra_vertex_attrib(draw, sn, si);

         /* add this slot to the texcoord-gen list */
         wide->texcoord_gen_slot[wide->num_texcoord_gen++] = slot;
      }
   }

   wide->psize_slot = -1;
   if (rast->point_size_per_vertex) {
      /* find PSIZ vertex output */
      wide->psize_slot = draw_find_shader_output(draw, TGSI_SEMANTIC_PSIZE, 0);
   }

   stage->point( stage, header );
}


static void widepoint_flush( struct draw_stage *stage, unsigned flags )
{
   struct draw_context *draw = stage->draw;
   struct pipe_context *pipe = draw->pipe;

   stage->point = widepoint_first_point;
   stage->next->flush( stage->next, flags );

   draw_remove_extra_vertex_attribs(draw);

   /* restore original rasterizer state */
   if (draw->rast_handle) {
      draw->suspend_flushing = TRUE;
      pipe->bind_rasterizer_state(pipe, draw->rast_handle);
      draw->suspend_flushing = FALSE;
   }
}


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


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


struct draw_stage *draw_wide_point_stage( struct draw_context *draw )
{
   struct widepoint_stage *wide = CALLOC_STRUCT(widepoint_stage);
   if (!wide)
      goto fail;

   wide->stage.draw = draw;
   wide->stage.name = "wide-point";
   wide->stage.next = NULL;
   wide->stage.point = widepoint_first_point;
   wide->stage.line = draw_pipe_passthrough_line;
   wide->stage.tri = draw_pipe_passthrough_tri;
   wide->stage.flush = widepoint_flush;
   wide->stage.reset_stipple_counter = widepoint_reset_stipple_counter;
   wide->stage.destroy = widepoint_destroy;

   if (!draw_alloc_temp_verts( &wide->stage, 4 ))
      goto fail;

   wide->sprite_coord_semantic =
      draw->pipe->screen->get_param(draw->pipe->screen, PIPE_CAP_TGSI_TEXCOORD)
      ?
      TGSI_SEMANTIC_TEXCOORD : TGSI_SEMANTIC_GENERIC;

   return &wide->stage;

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

   return NULL;
}