- This->shadow = This->format != D3DFMT_INTZ && util_format_has_depth(
- util_format_description(This->base.info.format));
+ /* When a depth buffer is sampled, it is for shadow mapping, except for
+ * D3DFMT_INTZ, D3DFMT_DF16 and D3DFMT_DF24.
+ * In addition D3DFMT_INTZ can be used for both texturing and depth buffering
+ * if z write is disabled. This particular feature may not work for us in
+ * practice because OGL doesn't have that. However apparently it is known
+ * some cards have performance issues with this feature, so real apps
+ * shouldn't use it. */
+ This->shadow = (This->format != D3DFMT_INTZ && This->format != D3DFMT_DF16 &&
+ This->format != D3DFMT_DF24) &&
+ util_format_has_depth(util_format_description(This->base.info.format));