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/* $Id: t_vb_fog.c,v 1.1 2003-02-28 11:48:07 pj Exp $ */

/*

 * Mesa 3-D graphics library

 * Version:  4.1

 *

 * Copyright (C) 1999-2002  Brian Paul   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, sublicense,

 * 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 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 NONINFRINGEMENT.  IN NO EVENT SHALL

 * BRIAN PAUL 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.

 *

 * Authors:

 *    Keith Whitwell <keith@tungstengraphics.com>

 */

#include "glheader.h"

#include "colormac.h"

#include "context.h"

#include "macros.h"

#include "imports.h"

#include "mmath.h"

#include "mtypes.h"

#include "math/m_xform.h"

#include "t_context.h"

#include "t_pipeline.h"

struct fog_stage_data {

   GLvector4f fogcoord;         /* has actual storage allocated */

   GLvector4f input;            /* points into VB->EyePtr Z values */

};

#define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)

#define FOG_EXP_TABLE_SIZE 256

#define FOG_MAX (10.0)

#define EXP_FOG_MAX .0006595

#define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)

static GLfloat exp_table[FOG_EXP_TABLE_SIZE];

static GLfloat inited = 0;

#if 1

#define NEG_EXP( result, narg )                                         \

do {                                                                    \

   GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR));                       \

   GLint k = (GLint) f;                                                 \

   if (k > FOG_EXP_TABLE_SIZE-2)                                        \

      result = (GLfloat) EXP_FOG_MAX;                                   \

   else                                                                 \

      result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]);      \

} while (0)

#else

#define NEG_EXP( result, narg )                                 \

do {                                                            \

   result = exp(-narg);                                         \

} while (0)

#endif

static void init_static_data( void )

{

   GLfloat f = 0.0F;

   GLint i = 0;

   for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {

      exp_table[i] = (GLfloat) exp(-f);

   }

   inited = 1;

}

static void make_win_fog_coords( GLcontext *ctx, GLvector4f *out,

                                 const GLvector4f *in )

{

   GLfloat end  = ctx->Fog.End;

   GLfloat *v = in->start;

   GLuint stride = in->stride;

   GLuint n = in->count;

   GLfloat (*data)[4] = out->data;

   GLfloat d;

   GLuint i;

   out->count = in->count;

   switch (ctx->Fog.Mode) {

   case GL_LINEAR:

      if (ctx->Fog.Start == ctx->Fog.End)

         d = 1.0F;

      else

         d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);

      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {

         GLfloat f = (end - ABSF(*v)) * d;

         data[i][0] = CLAMP(f, 0.0F, 1.0F);

      }

      break;

   case GL_EXP:

      d = ctx->Fog.Density;

      for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride))

         NEG_EXP( data[i][0], d * ABSF(*v) );

      break;

   case GL_EXP2:

      d = ctx->Fog.Density*ctx->Fog.Density;

      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {

         GLfloat z = *v;

         NEG_EXP( data[i][0], d * z * z );

      }

      break;

   default:

      _mesa_problem(ctx, "Bad fog mode in make_fog_coord");

      return;

   }

}

static GLboolean run_fog_stage( GLcontext *ctx,

                                struct gl_pipeline_stage *stage )

{

   struct vertex_buffer *VB = &TNL_CONTEXT(ctx)->vb;

   struct fog_stage_data *store = FOG_STAGE_DATA(stage);

   GLvector4f *input;

   if (stage->changed_inputs == 0)

      return GL_TRUE;

   if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT) {

      /* fog computed from Z depth */

      /* source = VB->ObjPtr or VB->EyePtr coords */

      /* dest = VB->FogCoordPtr = fog stage private storage */

      VB->FogCoordPtr = &store->fogcoord;

      if (!ctx->_NeedEyeCoords) {

         const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;

         GLfloat plane[4];

         /* Use this to store calculated eye z values:

          */

         input = &store->fogcoord;

         plane[0] = m[2];

         plane[1] = m[6];

         plane[2] = m[10];

         plane[3] = m[14];

         /* Full eye coords weren't required, just calculate the

          * eye Z values.

          */

         _mesa_dotprod_tab[VB->ObjPtr->size]( (GLfloat *) input->data,

                                              4 * sizeof(GLfloat),

                                              VB->ObjPtr, plane );

         input->count = VB->ObjPtr->count;

      }

      else {

         input = &store->input;

         if (VB->EyePtr->size < 2)

            _mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );

         input->data = (GLfloat (*)[4]) &(VB->EyePtr->data[0][2]);

         input->start = VB->EyePtr->start+2;

         input->stride = VB->EyePtr->stride;

         input->count = VB->EyePtr->count;

      }

   }

   else {

      /* use glFogCoord() coordinates */

      /* source = VB->FogCoordPtr */

      input = VB->FogCoordPtr;

      /* dest = fog stage private storage */

      VB->FogCoordPtr = &store->fogcoord;

   }

   make_win_fog_coords( ctx, VB->FogCoordPtr, input );

   return GL_TRUE;

}

static void check_fog_stage( GLcontext *ctx, struct gl_pipeline_stage *stage )

{

   stage->active = ctx->Fog.Enabled && !ctx->VertexProgram.Enabled;

   if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT)

      stage->inputs = VERT_BIT_EYE;

   else

      stage->inputs = VERT_BIT_FOG;

}

/* Called the first time stage->run() is invoked.

 */

static GLboolean alloc_fog_data( GLcontext *ctx,

                                 struct gl_pipeline_stage *stage )

{

   TNLcontext *tnl = TNL_CONTEXT(ctx);

   struct fog_stage_data *store;

   stage->privatePtr = MALLOC(sizeof(*store));

   store = FOG_STAGE_DATA(stage);

   if (!store)

      return GL_FALSE;

   _mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );

   _mesa_vector4f_init( &store->input, 0, 0 );

   if (!inited)

      init_static_data();

   /* Now run the stage.

    */

   stage->run = run_fog_stage;

   return stage->run( ctx, stage );

}

static void free_fog_data( struct gl_pipeline_stage *stage )

{

   struct fog_stage_data *store = FOG_STAGE_DATA(stage);

   if (store) {

      _mesa_vector4f_free( &store->fogcoord );

      FREE( store );

      stage->privatePtr = NULL;

   }

}

const struct gl_pipeline_stage _tnl_fog_coordinate_stage =

{

   "build fog coordinates",     /* name */

   _NEW_FOG,                    /* check_state */

   _NEW_FOG,                    /* run_state */

   GL_FALSE,                    /* active? */

   0,                           /* inputs */

   VERT_BIT_FOG,                /* outputs */

   0,                           /* changed_inputs */

   NULL,                        /* private_data */

   free_fog_data,               /* dtr */

   check_fog_stage,             /* check */

   alloc_fog_data               /* run -- initially set to init. */

};