add prefer-texture-buffer

panda/src/display/config_display.cxx

@@ -87,13 +87,27 @@ ConfigVariableBool show_buffers
           "GraphicsWindows, if possible, so that their contents may be viewed "
           "interactively.  Handy during development of multipass algorithms."));
 
+ConfigVariableBool prefer_texture_buffer
+("prefer-texture-buffer", true,
+ PRC_DESC("Set this true to make GraphicsOutput::make_texture_buffer() always "
+          "try to create an offscreen buffer supporting render-to-texture, "
+          "if the graphics card claims to be able to support this feature.  "
+          "If the graphics card cannot support this feature, this option is "
+          "ignored.  This is usually the fastest way to render "
+          "to a texture, and it presumably does not consume any additional "
+          "framebuffer memory over a copy-to-texture operation (since "
+          "the texture and the buffer share the "
+          "same memory)."));
+
 ConfigVariableBool prefer_parasite_buffer
 ("prefer-parasite-buffer", true,
  PRC_DESC("Set this true to make GraphicsOutput::make_texture_buffer() try to "
-          "create a parasite buffer before it tries to create an offscreen "
-          "buffer.  This may be desired if you know your graphics API does not "
-          "support render-to-texture and you want to minimize "
-          "framebuffer memory."));
+          "create a ParasiteBuffer before it tries to create an offscreen "
+          "buffer (assuming it could not create a direct render buffer for "
+          "some reason).  This may reduce your graphics card memory "
+          "requirements by sharing memory with the framebuffer, but it can "
+          "cause problems if the user subsequently resizes the window "
+          "smaller than the buffer."));
 
 ConfigVariableBool prefer_single_buffer
 ("prefer-single-buffer", true,
@@ -101,7 +115,7 @@ ConfigVariableBool prefer_single_buffer
           "try to create a single-buffered offscreen buffer, before falling "
           "back to a double-buffered one (or whatever kind the source window "
           "has).  This is true by default to reduce waste of framebuffer "
-          "memory, but you may get a performance benefit by setting it to "
+          "memory, but you might get a performance benefit by setting it to "
           "false (since in that case the buffer can share a graphics context "
           "with the window)."));
 

panda/src/display/config_display.h

@@ -48,6 +48,7 @@ extern EXPCL_PANDA ConfigVariableString screenshot_extension;
 
 extern EXPCL_PANDA ConfigVariableBool show_buffers;
 
+extern EXPCL_PANDA ConfigVariableBool prefer_texture_buffer;
 extern EXPCL_PANDA ConfigVariableBool prefer_parasite_buffer;
 extern EXPCL_PANDA ConfigVariableBool prefer_single_buffer;
 

panda/src/display/graphicsOutput.cxx

@@ -448,8 +448,12 @@ make_texture_buffer(const string &name, int x_size, int y_size) {
 
   // If the user so indicated in the Config.prc file, try to create a
   // parasite buffer first.  We can only do this if the requested size
-  // fits within the available framebuffer size.
+  // fits within the available framebuffer size.  Also, don't do this
+  // if the GSG supports render-to-a-texture and prefer_texture_buffer
+  // is true, since using a ParasiteButter precludes
+  // render-to-a-texture.
   if (prefer_parasite_buffer && 
+      !(prefer_texture_buffer && gsg->get_supports_render_texture()) && 
       (x_size <= host->get_x_size() && y_size <= host->get_y_size())) {
     buffer = engine->make_parasite(host, name, sort, x_size, y_size);
     if (buffer != (GraphicsOutput *)NULL) {