s_texfilter.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

   ASSERT(tObj->WrapT==GL_REPEAT);
   ASSERT(img->Border==0);
   ASSERT(img->TexFormat->MesaFormat==MESA_FORMAT_RGB);
   ASSERT(img->_IsPowerOfTwo);

   for (k=0; k<n; k++) {
      GLint i = IFLOOR(texcoords[k][0] * width) & colMask;
      GLint j = IFLOOR(texcoords[k][1] * height) & rowMask;
      GLint pos = (j << shift) | i;
      GLchan *texel = ((GLchan *) img->Data) + 3*pos;
      rgba[k][RCOMP] = texel[0];
      rgba[k][GCOMP] = texel[1];
      rgba[k][BCOMP] = texel[2];
   }
}


/*
 * Optimized 2-D texture sampling:
 *    S and T wrap mode == GL_REPEAT
 *    GL_NEAREST min/mag filter
 *    No border
 *    RowStride == Width,
 *    Format = GL_RGBA
 */
static void
opt_sample_rgba_2d( GLcontext *ctx,
                    const struct gl_texture_object *tObj,
                    GLuint n, const GLfloat texcoords[][4],
                    const GLfloat lambda[], GLchan rgba[][4] )
{
   const struct gl_texture_image *img = tObj->Image[0][tObj->BaseLevel];
   const GLfloat width = (GLfloat) img->Width;
   const GLfloat height = (GLfloat) img->Height;
   const GLint colMask = img->Width - 1;
   const GLint rowMask = img->Height - 1;
   const GLint shift = img->WidthLog2;
   GLuint i;
   (void) ctx;
   (void) lambda;
   ASSERT(tObj->WrapS==GL_REPEAT);
   ASSERT(tObj->WrapT==GL_REPEAT);
   ASSERT(img->Border==0);
   ASSERT(img->TexFormat->MesaFormat==MESA_FORMAT_RGBA);
   ASSERT(img->_IsPowerOfTwo);

   for (i = 0; i < n; i++) {
      const GLint col = IFLOOR(texcoords[i][0] * width) & colMask;
      const GLint row = IFLOOR(texcoords[i][1] * height) & rowMask;
      const GLint pos = (row << shift) | col;
      const GLchan *texel = ((GLchan *) img->Data) + (pos << 2);    /* pos*4 */
      COPY_CHAN4(rgba[i], texel);
   }
}


/*
 * Given an array of texture coordinate and lambda (level of detail)
 * values, return an array of texture sample.
 */
static void
sample_lambda_2d( GLcontext *ctx,
                  const struct gl_texture_object *tObj,
                  GLuint n, const GLfloat texcoords[][4],
                  const GLfloat lambda[], GLchan rgba[][4] )
{
   const struct gl_texture_image *tImg = tObj->Image[0][tObj->BaseLevel];
   GLuint minStart, minEnd;  /* texels with minification */
   GLuint magStart, magEnd;  /* texels with magnification */

   const GLboolean repeatNoBorderPOT = (tObj->WrapS == GL_REPEAT)
      && (tObj->WrapT == GL_REPEAT)
      && (tImg->Border == 0 && (tImg->Width == tImg->RowStride))
      && (tImg->TexFormat->BaseFormat != GL_COLOR_INDEX)
      && tImg->_IsPowerOfTwo;

   ASSERT(lambda != NULL);
   compute_min_mag_ranges(tObj, n, lambda,
                          &minStart, &minEnd, &magStart, &magEnd);

   if (minStart < minEnd) {
      /* do the minified texels */
      const GLuint m = minEnd - minStart;
      switch (tObj->MinFilter) {
      case GL_NEAREST:
         if (repeatNoBorderPOT) {
            switch (tImg->TexFormat->MesaFormat) {
            case MESA_FORMAT_RGB:
               opt_sample_rgb_2d(ctx, tObj, m, texcoords + minStart,
                                 NULL, rgba + minStart);
               break;
            case MESA_FORMAT_RGBA:
	       opt_sample_rgba_2d(ctx, tObj, m, texcoords + minStart,
                                  NULL, rgba + minStart);
               break;
            default:
               sample_nearest_2d(ctx, tObj, m, texcoords + minStart,
                                 NULL, rgba + minStart );
            }
         }
         else {
            sample_nearest_2d(ctx, tObj, m, texcoords + minStart,
                              NULL, rgba + minStart);
         }
         break;
      case GL_LINEAR:
	 sample_linear_2d(ctx, tObj, m, texcoords + minStart,
			  NULL, rgba + minStart);
         break;
      case GL_NEAREST_MIPMAP_NEAREST:
         sample_2d_nearest_mipmap_nearest(ctx, tObj, m,
                                          texcoords + minStart,
                                          lambda + minStart, rgba + minStart);
         break;
      case GL_LINEAR_MIPMAP_NEAREST:
         sample_2d_linear_mipmap_nearest(ctx, tObj, m, texcoords + minStart,
                                         lambda + minStart, rgba + minStart);
         break;
      case GL_NEAREST_MIPMAP_LINEAR:
         sample_2d_nearest_mipmap_linear(ctx, tObj, m, texcoords + minStart,
                                         lambda + minStart, rgba + minStart);
         break;
      case GL_LINEAR_MIPMAP_LINEAR:
         if (repeatNoBorderPOT)
            sample_2d_linear_mipmap_linear_repeat(ctx, tObj, m,
                  texcoords + minStart, lambda + minStart, rgba + minStart);
         else
            sample_2d_linear_mipmap_linear(ctx, tObj, m, texcoords + minStart,
                                        lambda + minStart, rgba + minStart);
         break;
      default:
         _mesa_problem(ctx, "Bad min filter in sample_2d_texture");
         return;
      }
   }

   if (magStart < magEnd) {
      /* do the magnified texels */
      const GLuint m = magEnd - magStart;

      switch (tObj->MagFilter) {
      case GL_NEAREST:
         if (repeatNoBorderPOT) {
            switch (tImg->TexFormat->MesaFormat) {
            case MESA_FORMAT_RGB:
               opt_sample_rgb_2d(ctx, tObj, m, texcoords + magStart,
                                 NULL, rgba + magStart);
               break;
            case MESA_FORMAT_RGBA:
	       opt_sample_rgba_2d(ctx, tObj, m, texcoords + magStart,
                                  NULL, rgba + magStart);
               break;
            default:
               sample_nearest_2d(ctx, tObj, m, texcoords + magStart,
                                 NULL, rgba + magStart );
            }
         }
         else {
            sample_nearest_2d(ctx, tObj, m, texcoords + magStart,
                              NULL, rgba + magStart);
         }
         break;
      case GL_LINEAR:
	 sample_linear_2d(ctx, tObj, m, texcoords + magStart,
			  NULL, rgba + magStart);
         break;
      default:
         _mesa_problem(ctx, "Bad mag filter in sample_lambda_2d");
      }
   }
}



/**********************************************************************/
/*                    3-D Texture Sampling Functions                  */
/**********************************************************************/

/*
 * Return the texture sample for coordinate (s,t,r) using GL_NEAREST filter.
 */
static void
sample_3d_nearest(GLcontext *ctx,
                  const struct gl_texture_object *tObj,
                  const struct gl_texture_image *img,
                  const GLfloat texcoord[4],
                  GLchan rgba[4])
{
   const GLint width = img->Width2;     /* without border, power of two */
   const GLint height = img->Height2;   /* without border, power of two */
   const GLint depth = img->Depth2;     /* without border, power of two */
   GLint i, j, k;
   (void) ctx;

   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width,  i);
   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoord[1], height, j);
   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapR, texcoord[2], depth,  k);

   if (i < 0 || i >= (GLint) img->Width ||
       j < 0 || j >= (GLint) img->Height ||
       k < 0 || k >= (GLint) img->Depth) {
      /* Need this test for GL_CLAMP_TO_BORDER mode */
      COPY_CHAN4(rgba, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i, j, k, rgba);
   }
}



/*
 * Return the texture sample for coordinate (s,t,r) using GL_LINEAR filter.
 */
static void
sample_3d_linear(GLcontext *ctx,
                 const struct gl_texture_object *tObj,
                 const struct gl_texture_image *img,
                 const GLfloat texcoord[4],
                 GLchan rgba[4])
{
   const GLint width = img->Width2;
   const GLint height = img->Height2;
   const GLint depth = img->Depth2;
   GLint i0, j0, k0, i1, j1, k1;
   GLbitfield useBorderColor = 0x0;
   GLfloat u, v, w;
   GLfloat a, b, c;
   GLchan t000[4], t010[4], t001[4], t011[4];
   GLchan t100[4], t110[4], t101[4], t111[4];

   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width,  i0, i1);
   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoord[1], v, height, j0, j1);
   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapR, texcoord[2], w, depth,  k0, k1);

   if (img->Border) {
      i0 += img->Border;
      i1 += img->Border;
      j0 += img->Border;
      j1 += img->Border;
      k0 += img->Border;
      k1 += img->Border;
   }
   else {
      /* check if sampling texture border color */
      if (i0 < 0 || i0 >= width)   useBorderColor |= I0BIT;
      if (i1 < 0 || i1 >= width)   useBorderColor |= I1BIT;
      if (j0 < 0 || j0 >= height)  useBorderColor |= J0BIT;
      if (j1 < 0 || j1 >= height)  useBorderColor |= J1BIT;
      if (k0 < 0 || k0 >= depth)   useBorderColor |= K0BIT;
      if (k1 < 0 || k1 >= depth)   useBorderColor |= K1BIT;
   }

   /* Fetch texels */
   if (useBorderColor & (I0BIT | J0BIT | K0BIT)) {
      COPY_CHAN4(t000, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i0, j0, k0, t000);
   }
   if (useBorderColor & (I1BIT | J0BIT | K0BIT)) {
      COPY_CHAN4(t100, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i1, j0, k0, t100);
   }
   if (useBorderColor & (I0BIT | J1BIT | K0BIT)) {
      COPY_CHAN4(t010, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i0, j1, k0, t010);
   }
   if (useBorderColor & (I1BIT | J1BIT | K0BIT)) {
      COPY_CHAN4(t110, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i1, j1, k0, t110);
   }

   if (useBorderColor & (I0BIT | J0BIT | K1BIT)) {
      COPY_CHAN4(t001, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i0, j0, k1, t001);
   }
   if (useBorderColor & (I1BIT | J0BIT | K1BIT)) {
      COPY_CHAN4(t101, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i1, j0, k1, t101);
   }
   if (useBorderColor & (I0BIT | J1BIT | K1BIT)) {
      COPY_CHAN4(t011, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i0, j1, k1, t011);
   }
   if (useBorderColor & (I1BIT | J1BIT | K1BIT)) {
      COPY_CHAN4(t111, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i1, j1, k1, t111);
   }

   /* trilinear interpolation of samples */
   a = FRAC(u);
   b = FRAC(v);
   c = FRAC(w);
   lerp_rgba_3d(rgba, a, b, c, t000, t100, t010, t110, t001, t101, t011, t111);
}



static void
sample_3d_nearest_mipmap_nearest(GLcontext *ctx,
                                 const struct gl_texture_object *tObj,
                                 GLuint n, const GLfloat texcoord[][4],
                                 const GLfloat lambda[], GLchan rgba[][4] )
{
   GLuint i;
   for (i = 0; i < n; i++) {
      GLint level = nearest_mipmap_level(tObj, lambda[i]);
      sample_3d_nearest(ctx, tObj, tObj->Image[0][level], texcoord[i], rgba[i]);
   }
}


static void
sample_3d_linear_mipmap_nearest(GLcontext *ctx,
                                const struct gl_texture_object *tObj,
                                GLuint n, const GLfloat texcoord[][4],
                                const GLfloat lambda[], GLchan rgba[][4])
{
   GLuint i;
   ASSERT(lambda != NULL);
   for (i = 0; i < n; i++) {
      GLint level = nearest_mipmap_level(tObj, lambda[i]);
      sample_3d_linear(ctx, tObj, tObj->Image[0][level], texcoord[i], rgba[i]);
   }
}


static void
sample_3d_nearest_mipmap_linear(GLcontext *ctx,
                                const struct gl_texture_object *tObj,
                                GLuint n, const GLfloat texcoord[][4],
                                const GLfloat lambda[], GLchan rgba[][4])
{
   GLuint i;
   ASSERT(lambda != NULL);
   for (i = 0; i < n; i++) {
      GLint level = linear_mipmap_level(tObj, lambda[i]);
      if (level >= tObj->_MaxLevel) {
         sample_3d_nearest(ctx, tObj, tObj->Image[0][tObj->_MaxLevel],
                           texcoord[i], rgba[i]);
      }
      else {
         GLchan t0[4], t1[4];  /* texels */
         const GLfloat f = FRAC(lambda[i]);
         sample_3d_nearest(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
         sample_3d_nearest(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
         lerp_rgba(rgba[i], f, t0, t1);
      }
   }
}


static void
sample_3d_linear_mipmap_linear(GLcontext *ctx,
                               const struct gl_texture_object *tObj,
                               GLuint n, const GLfloat texcoord[][4],
                               const GLfloat lambda[], GLchan rgba[][4])
{
   GLuint i;
   ASSERT(lambda != NULL);
   for (i = 0; i < n; i++) {
      GLint level = linear_mipmap_level(tObj, lambda[i]);
      if (level >= tObj->_MaxLevel) {
         sample_3d_linear(ctx, tObj, tObj->Image[0][tObj->_MaxLevel],
                          texcoord[i], rgba[i]);
      }
      else {
         GLchan t0[4], t1[4];  /* texels */
         const GLfloat f = FRAC(lambda[i]);
         sample_3d_linear(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
         sample_3d_linear(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
         lerp_rgba(rgba[i], f, t0, t1);
      }
   }
}


static void
sample_nearest_3d(GLcontext *ctx,
                  const struct gl_texture_object *tObj, GLuint n,
                  const GLfloat texcoords[][4], const GLfloat lambda[],
                  GLchan rgba[][4])
{
   GLuint i;
   struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
   (void) lambda;
   for (i=0;i<n;i++) {
      sample_3d_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
   }
}



static void
sample_linear_3d( GLcontext *ctx,
                  const struct gl_texture_object *tObj, GLuint n,