Allow dimensions to be specified when creating a render target.

PiperOrigin-RevId: 907622395
Change-Id: I0f806f4d77afa6a178a20d36dae3e96b81359494

src/experimental/filament/compat/mjr_filament_renderer.cc

@@ -134,11 +134,12 @@ void MjrFilamentRenderer::ReadPixels(mjrRect viewport, unsigned char* rgb,
   if (rgb) {
     mjrRenderTargetConfig config;
     mjr_defaultRenderTargetConfig(&config);
+    config.width = viewport.width;
+    config.height = viewport.height;
     config.color_format = mjPIXEL_FORMAT_RGB8;
     config.depth_format = mjPIXEL_FORMAT_DEPTH32F;
     auto target =
         std::make_unique<RenderTarget>(filament_context_.get(), config);
-    target->Prepare(viewport.width, viewport.height);
     render_requests_[0].target = target.get();
     render_requests_[1].target = target.get();
 

src/experimental/filament/filament/render_target.cc

@@ -34,7 +34,11 @@ namespace mujoco {
 
 RenderTarget::RenderTarget(FilamentContext* ctx,
                            const mjrRenderTargetConfig& config)
-    : ctx_(ctx), config_(config) {}
+    : ctx_(ctx), config_(config) {
+  if (config_.width > 0 && config_.height > 0) {
+    Prepare(config_.width, config_.height);
+  }
+}
 
 RenderTarget::~RenderTarget() noexcept {
   Destroy();
@@ -47,6 +51,11 @@ void RenderTarget::Prepare(int width, int height) {
   Destroy();
   width_ = width;
   height_ = height;
+  if (width_ <= 0 || height_ <= 0) {
+    width_ = 0;
+    height_ = 0;
+    return;
+  }
 
   mjrTextureConfig color_config;
   mjr_defaultTextureConfig(&color_config);

src/experimental/filament/render_context_filament.cc

@@ -116,6 +116,7 @@ void mjr_defaultRenderableParams(mjrRenderableParams* params) {
 }
 
 void mjr_defaultRenderTargetConfig(mjrRenderTargetConfig* config) {
+  memset(config, 0, sizeof(mjrRenderTargetConfig));
   config->color_format = mjPIXEL_FORMAT_RGBA8;
   config->depth_format = mjPIXEL_FORMAT_DEPTH32F;
 }

src/experimental/filament/render_context_filament.h

@@ -326,7 +326,13 @@ void mjr_defaultLightParams(mjrLightParams* params);
 
 // Defines the basic properties of a render target.
 struct mjrRenderTargetConfig {
+  // The width of the render target.
+  int width;
+  // The height of the render target.
+  int height;
+  // The format of the color buffer in the render target.
   mjrPixelFormat color_format;
+  // The format of the depth buffer in the render target.
   mjrPixelFormat depth_format;
 };