src/gallium/auxiliary/util/u_sampler.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2010 VMware, Inc.
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  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
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  26  **************************************************************************/
  27
  28
  29 #include "u_format.h"
  30 #include "u_sampler.h"
  31
  32
  33 /**
  34  * Initialize a pipe_sampler_view.  'view' is considered to have
  35  * uninitialized contents.
  36  */
  37 static void
  38 default_template(struct pipe_sampler_view *view,
  39                  const struct pipe_resource *texture,
  40                  enum pipe_format format,
  41                  unsigned expand_green_blue)
  42 {
  43    memset(view, 0, sizeof(*view));
  44
  45    /* XXX: Check if format is compatible with texture->format.
  46     */
  47
  48    view->format = format;
  49    view->u.tex.first_level = 0;
  50    view->u.tex.last_level = texture->last_level;
  51    view->u.tex.first_layer = 0;
  52    view->u.tex.last_layer = texture->target == PIPE_TEXTURE_3D ?
  53                                texture->depth0 - 1 : texture->array_size - 1;
  54    view->swizzle_r = PIPE_SWIZZLE_RED;
  55    view->swizzle_g = PIPE_SWIZZLE_GREEN;
  56    view->swizzle_b = PIPE_SWIZZLE_BLUE;
  57    view->swizzle_a = PIPE_SWIZZLE_ALPHA;
  58
  59    /* Override default green and blue component expansion to the requested
  60     * one.
  61     *
  62     * Gallium expands nonexistent components to (0,0,0,1), DX9 expands
  63     * to (1,1,1,1).  Since alpha is always expanded to 1, and red is
  64     * always present, we only really care about green and blue
  65     * components.
  66     *
  67     * To make it look less hackish, one would have to add
  68     * UTIL_FORMAT_SWIZZLE_EXPAND to indicate components for expansion
  69     * and then override without exceptions or favoring one component
  70     * over another.
  71     */
  72    if (format != PIPE_FORMAT_A8_UNORM) {
  73       const struct util_format_description *desc = util_format_description(format);
  74
  75       assert(desc);
  76       if (desc) {
  77          if (desc->swizzle[1] == UTIL_FORMAT_SWIZZLE_0) {
  78             view->swizzle_g = expand_green_blue;
  79          }
  80          if (desc->swizzle[2] == UTIL_FORMAT_SWIZZLE_0) {
  81             view->swizzle_b = expand_green_blue;
  82          }
  83       }
  84    }
  85 }
  86
  87 void
  88 u_sampler_view_default_template(struct pipe_sampler_view *view,
  89                                 const struct pipe_resource *texture,
  90                                 enum pipe_format format)
  91 {
  92    /* Expand to (0, 0, 0, 1) */
  93    default_template(view,
  94                     texture,
  95                     format,
  96                     PIPE_SWIZZLE_ZERO);
  97 }
  98
  99 void
 100 u_sampler_view_default_dx9_template(struct pipe_sampler_view *view,
 101                                     const struct pipe_resource *texture,
 102                                     enum pipe_format format)
 103 {
 104    /* Expand to (1, 1, 1, 1) */
 105    default_template(view,
 106                     texture,
 107                     format,
 108                     PIPE_SWIZZLE_ONE);
 109 }