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Optimized MDL clipping (in software)

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Optimized MDL clipping (in software)

Postby mankrip » Thu Sep 12, 2013 6:00 am

This one is easy. Just replace the whole r_aclip.c (mdl_clip.c, in Makaqu) file with this:
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/*
Copyright (C) 1996-1997 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
// r_aclip.c: clip routines for drawing Alias models directly to the screen

#include "quakedef.h"
#include "r_local.h"
#include "d_local.h"

static finalvert_t
   fv[2][8]
,   * clipfv // mankrip
   ;
static auxvert_t
   av[8]
   ;
// mankrip - begin
#define HORIZONTAL 0 // for clipplane
#define VERTICAL 1 // for clipplane
static int
   * clipfvi0
,   * clipfvi1
,   clipplane // for clipscale
,   cliplimit // for clipscale
   ;
static float
   clipscale
   ;
static vec3_t
   clipv0
,   clipv1
   ;
// mankrip - end



/*
================
R_Alias_clip_z

pfv0 is the unclipped vertex, pfv1 is the z-clipped vertex
================
*/
void R_Alias_clip_z (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
   // mankrip - begin
   static auxvert_t
      avout
      ;
   if (pfv0->v[1] >= pfv1->v[1])
   {
      clipfvi0 = pfv0->v;
      clipfvi1 = pfv1->v;
      // copying these integer vectors also implicitely typecasts them
      VectorCopy (av[pfv0 - &fv[0][0]].fv, clipv0);
      VectorCopy (av[pfv1 - &fv[0][0]].fv, clipv1);
   }
   else
   {
      clipfvi0 = pfv1->v;
      clipfvi1 = pfv0->v;
      // copying these integer vectors also implicitely typecasts them
      VectorCopy (av[pfv1 - &fv[0][0]].fv, clipv0);
      VectorCopy (av[pfv0 - &fv[0][0]].fv, clipv1);
   }
   clipscale = (ALIAS_Z_CLIP_PLANE - clipv0[2]) / (clipv1[2] - clipv0[2]);

   avout.fv[0] = (int) (clipv0[0] + (clipv1[0] - clipv0[0]) * clipscale);
   avout.fv[1] = (int) (clipv0[1] + (clipv1[1] - clipv0[1]) * clipscale);
   avout.fv[2] = ALIAS_Z_CLIP_PLANE;

   out->v[2] =   clipfvi0[2] + (int) ( (float) (clipfvi1[2] - clipfvi0[2]) * clipscale);
   out->v[3] =   clipfvi0[3] + (int) ( (float) (clipfvi1[3] - clipfvi0[3]) * clipscale);
   out->v[4] =   clipfvi0[4] + (int) ( (float) (clipfvi1[4] - clipfvi0[4]) * clipscale);
   // mankrip - end

   R_AliasProjectFinalVert (out, &avout);
}



// mankrip - begin
void R_Alias_clip_xy (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out)
{
   // for left/right/top/bottom variations, only clipscale changes
   // r_refdef.vrect.x for left cliplimit, r_refdef.vrectright for right cliplimit
   // r_refdef.vrect.y for top cliplimit, r_refdef.vrectbottom for bottom cliplimit
   // clipplane should be either zero (horizontal) or 1 (vertical)

   if (pfv0->v[1] >= pfv1->v[1])
   {
      clipfvi0 = pfv0->v;
      clipfvi1 = pfv1->v;
   }
   else
   {
      clipfvi0 = pfv1->v;
      clipfvi1 = pfv0->v;
   }
   clipscale = (float) (cliplimit - clipfvi0[clipplane]) / (float) (clipfvi1[clipplane] - clipfvi0[clipplane]);
   out->v[0] = clipfvi0[0] + (int) ( (float) (clipfvi1[0] - clipfvi0[0]) * clipscale + 0.5f);
   out->v[1] = clipfvi0[1] + (int) ( (float) (clipfvi1[1] - clipfvi0[1]) * clipscale + 0.5f);
   out->v[2] = clipfvi0[2] + (int) ( (float) (clipfvi1[2] - clipfvi0[2]) * clipscale + 0.5f);
   out->v[3] = clipfvi0[3] + (int) ( (float) (clipfvi1[3] - clipfvi0[3]) * clipscale + 0.5f);
   out->v[4] = clipfvi0[4] + (int) ( (float) (clipfvi1[4] - clipfvi0[4]) * clipscale + 0.5f);
   out->v[5] = clipfvi0[5] + (int) ( (float) (clipfvi1[5] - clipfvi0[5]) * clipscale + 0.5f);
}
// mankrip - end



int R_AliasClip (finalvert_t *in, finalvert_t *out, int flag, int count,
   void (*clip) (finalvert_t *pfv0, finalvert_t *pfv1, finalvert_t *out) )
{
   static int
      i
   ,   j
   ,   k
   ,   flags
   ,   oldflags
      ;

   for (k = 0 , i = 0 , j = count - 1 ; i < count ; j = i, i++)
   {
      oldflags = in[j].flags & flag;
      flags    = in[i].flags & flag;

      if (flags && oldflags)
         continue;
      if (oldflags ^ flags)
      {
         clip (&in[j], &in[i], &out[k]);
         out[k].flags = 0;

         // check if it needs to be clipped again
         // mankrip - initial clipping is done right-to-left and bottom-to-top, so let's check the other way around now
         if (out[k].v[0] < r_refdef.vrect.x)      out[k].flags |= ALIAS_LEFT_CLIP;
         else
         if (out[k].v[0] > r_refdef.vrectright)   out[k].flags |= ALIAS_RIGHT_CLIP;
         if (out[k].v[1] < r_refdef.vrect.y)      out[k].flags |= ALIAS_TOP_CLIP;
         else
         if (out[k].v[1] > r_refdef.vrectbottom) out[k].flags |= ALIAS_BOTTOM_CLIP;

         k++;
      }
      if (!flags)
      {
         out[k] = in[i];
         k++;
      }
   }
   return k;
}



void R_AliasClipTriangle (mtriangle_t *ptri)
{
   static int
      i
   ,   k
   ,   pingpong
      ;
   static unsigned
      clipflags
      ;
   static mtriangle_t
      mtri
      ;

   // copy vertexes and fix seam texture coordinates
   fv[0][0] = pfinalverts[ptri->vertindex[0]];
   fv[0][1] = pfinalverts[ptri->vertindex[1]];
   fv[0][2] = pfinalverts[ptri->vertindex[2]];
   // mankrip - begin
   if (!ptri->facesfront)
   {
      if (fv[0][0].flags & ALIAS_ONSEAM) fv[0][0].v[2] += r_affinetridesc.seamfixupX16;
      if (fv[0][1].flags & ALIAS_ONSEAM) fv[0][1].v[2] += r_affinetridesc.seamfixupX16;
      if (fv[0][2].flags & ALIAS_ONSEAM) fv[0][2].v[2] += r_affinetridesc.seamfixupX16;
   }
   // mankrip - end

   // clip
   clipflags = fv[0][0].flags | fv[0][1].flags | fv[0][2].flags;

   if (clipflags & ALIAS_Z_CLIP)
   {
      av[0] = pauxverts[ptri->vertindex[0]];
      av[1] = pauxverts[ptri->vertindex[1]];
      av[2] = pauxverts[ptri->vertindex[2]];

      k = R_AliasClip (fv[0], fv[1], ALIAS_Z_CLIP, 3, R_Alias_clip_z);
      if (k == 0)
         return;
      pingpong = 1;
      clipflags = fv[1][0].flags | fv[1][1].flags | fv[1][2].flags;
   }
   else
   {
      pingpong = 0;
      k = 3;
   }

   // mankrip - the viewmodel is always on the bottom of the screen, so let's clip the bottom first
   if (clipflags & ALIAS_BOTTOM_CLIP)
   {
      cliplimit = r_refdef.vrectbottom; // mankrip
      clipplane = VERTICAL; // mankrip
      k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1], ALIAS_BOTTOM_CLIP, k, R_Alias_clip_xy);
      if (k == 0)
         return;
      pingpong ^= 1;
   }

   // mankrip - weapons such as the axe are right-handed, so let's clip the right before the left
   if (clipflags & ALIAS_RIGHT_CLIP)
   {
      cliplimit = r_refdef.vrectright; // mankrip
      clipplane = HORIZONTAL; // mankrip
      k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1], ALIAS_RIGHT_CLIP, k, R_Alias_clip_xy);
      if (k == 0)
         return;
      pingpong ^= 1;
   }

   if (clipflags & ALIAS_TOP_CLIP)
   {
      cliplimit = r_refdef.vrect.y; // mankrip
      clipplane = VERTICAL; // mankrip
      k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1], ALIAS_TOP_CLIP, k, R_Alias_clip_xy);
      if (k == 0)
         return;
      pingpong ^= 1;
   }

   if (clipflags & ALIAS_LEFT_CLIP)
   {
      cliplimit = r_refdef.vrect.x; // mankrip
      clipplane = HORIZONTAL; // mankrip
      k = R_AliasClip (fv[pingpong], fv[pingpong ^ 1], ALIAS_LEFT_CLIP, k, R_Alias_clip_xy);
      if (k == 0)
         return;
      pingpong ^= 1;
   }

   // mankrip - fix any rounding that went outside of the screen
   for (i = 0 ; i < k ; i++)
   {
      clipfvi0 = fv[pingpong][i].v;
      if (clipfvi0[0] > r_refdef.vrectright)
         clipfvi0[0] = r_refdef.vrectright;
      else
      if (clipfvi0[0] < r_refdef.vrect.x)
         clipfvi0[0] = r_refdef.vrect.x;

      if (clipfvi0[1] > r_refdef.vrectbottom)
         clipfvi0[1] = r_refdef.vrectbottom;
      else
      if (clipfvi0[1] < r_refdef.vrect.y)
         clipfvi0[1] = r_refdef.vrect.y;
      // mankrip - begin
      if (currententity->scrleft  > clipfvi0[0])
         currententity->scrleft  = clipfvi0[0];
      if (currententity->scrright < clipfvi0[0])
         currententity->scrright = clipfvi0[0];
      if (currententity->scrtop    > clipfvi0[1])
         currententity->scrtop    = clipfvi0[1];
      if (currententity->scrbottom < clipfvi0[1])
         currententity->scrbottom = clipfvi0[1];
      // mankrip - end

      fv[pingpong][i].flags = 0;
   }

   // draw triangles
   mtri.facesfront = ptri->facesfront;
   r_affinetridesc.ptriangles = &mtri;
   r_affinetridesc.pfinalverts = fv[pingpong];

   // FIXME: do all at once as trifan?
   mtri.vertindex[0] = 0;
   for (i = 1 ; i < k - 1 ; i++)
   {
      mtri.vertindex[1] = i;
      mtri.vertindex[2] = i+1;
      D_PolysetDraw_C (); // mankrip - transparencies - edited
   }
}

I've unrolled a number of loops and employed some other strategies to gain speed, but on the other hand, to make the code easier to maintain (and to read!) I've collapsed the four top/bottom/left/right clipping functions into one (R_Alias_clip_xy), which requires cliplimit and clipplane to be set before each call.

I haven't benchmarked the speed difference in comparison to the original C code, as my main goal with this was to understand how the MDL clipping works.
Ph'nglui mglw'nafh mankrip Hell's end wgah'nagl fhtagn.
==-=-=-=-=-=-=-=-=-=-==
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mankrip
 
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Joined: Fri Jul 04, 2008 3:02 am

Re: Optimized MDL clipping (in software)

Postby qbism » Fri Sep 13, 2013 2:38 am

Well, in a quick timedemo comparison it works and is at least not slower. I did not do a vigorous benchmark with a lot of mdl flesh in the scene.
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