2 files changed, 55 insertions, 4 deletions

diff --git a/indra/llrender/llrendertarget.cpp b/indra/llrender/llrendertarget.cpp
index d9520b3bf6..f0df3bcf90 100644
--- a/indra/llrender/llrendertarget.cpp
+++ b/indra/llrender/llrendertarget.cpp
@@ -61,8 +61,11 @@ BOOL LLRenderTarget::sUseFBO = FALSE;
 LLRenderTarget::LLRenderTarget() :
 	mResX(0),
 	mResY(0),
+	mViewportWidth(0),
+	mViewportHeight(0),
 	mTex(0),
 	mFBO(0),
+	mColorFmt(0),
 	mDepth(0),
 	mStencil(0),
 	mUseDepth(FALSE),
@@ -86,13 +89,31 @@ void LLRenderTarget::setSampleBuffer(LLMultisampleBuffer* buffer)
 
 void LLRenderTarget::allocate(U32 resx, U32 resy, U32 color_fmt, BOOL depth, BOOL stencil, LLTexUnit::eTextureType usage, BOOL use_fbo)
 {
+	// only reallocate if something changed
+	if (mResX == resx
+		&& mResY == resy
+		&& mUseDepth == depth
+		&& mStencil == stencil
+		&& mUsage == usage
+		&& (mFBO != 0) == ((sUseFBO || use_fbo) && gGLManager.mHasFramebufferObject)
+		&& mColorFmt == color_fmt)
+	{
+		// nothing to do
+		return;
+	}
+		
 	stop_glerror();
 	mResX = resx;
 	mResY = resy;
+	// default viewport to entire texture
+	mViewportWidth = mResX;
+	mViewportHeight = mResY;
 
 	mStencil = stencil;
 	mUsage = usage;
 	mUseDepth = depth;
+	mFBO = 0;
+	mColorFmt = color_fmt;
 
 	release();
 
@@ -312,7 +333,7 @@ void LLRenderTarget::bindTarget()
 		}
 	}
 
-	glViewport(0, 0, mResX, mResY);
+	glViewport(0, 0, mViewportWidth, mViewportHeight);
 	sBoundTarget = this;
 }
 
@@ -515,12 +536,18 @@ BOOL LLRenderTarget::isComplete() const
 	return (!mTex.empty() || mDepth) ? TRUE : FALSE;
 }
 
+void LLRenderTarget::setViewport(U32 width, U32 height)
+{
+	mViewportWidth = llmin(width, mResX);
+	mViewportHeight = llmin(height, mResY);
+}
+
 void LLRenderTarget::getViewport(S32* viewport)
 {
 	viewport[0] = 0;
 	viewport[1] = 0;
-	viewport[2] = mResX;
-	viewport[3] = mResY;
+	viewport[2] = mViewportWidth;
+	viewport[3] = mViewportHeight;
 }
 
 //==================================================
@@ -581,7 +608,7 @@ void LLMultisampleBuffer::bindTarget(LLRenderTarget* ref)
 
 	check_framebuffer_status();
 
-	glViewport(0, 0, mResX, mResY);
+	glViewport(0, 0, mViewportWidth, mViewportHeight);
 
 	sBoundTarget = this;
 }
@@ -593,13 +620,30 @@ void LLMultisampleBuffer::allocate(U32 resx, U32 resy, U32 color_fmt, BOOL depth
 
 void LLMultisampleBuffer::allocate(U32 resx, U32 resy, U32 color_fmt, BOOL depth, BOOL stencil,  LLTexUnit::eTextureType usage, BOOL use_fbo, U32 samples )
 {
+	if (mResX == resx
+		&& mResY == resy
+		&& mUseDepth == depth
+		&& mStencil == stencil
+		&& mUsage == usage
+		&& (mFBO != 0) == ((sUseFBO || use_fbo) && gGLManager.mHasFramebufferObject)
+		&& mColorFmt == color_fmt
+		&& mSamples == samples)
+	{
+		// nothing to do
+		return;
+	}
+
 	stop_glerror();
 	mResX = resx;
 	mResY = resy;
+	mViewportWidth = mResX;
+	mViewportHeight = mResY;
 
 	mUsage = usage;
 	mUseDepth = depth;
 	mStencil = stencil;
+	mFBO = 0;
+	mColorFmt = color_fmt;
 
 	releaseSampleBuffer();
 
diff --git a/indra/llrender/llrendertarget.h b/indra/llrender/llrendertarget.h
index b7ebfc8f7f..125747424c 100644
--- a/indra/llrender/llrendertarget.h
+++ b/indra/llrender/llrendertarget.h
@@ -107,6 +107,9 @@ public:
 	//uses scissor rect if in copy-to-texture mode
 	void clear(U32 mask = 0xFFFFFFFF);
 	
+	// override default viewport to a smaller size
+	void setViewport(U32 width, U32 height);
+
 	//get applied viewport
 	void getViewport(S32* viewport);
 
@@ -150,12 +153,16 @@ protected:
 	friend class LLMultisampleBuffer;
 	U32 mResX;
 	U32 mResY;
+	U32 mViewportWidth;
+	U32 mViewportHeight;
 	std::vector<U32> mTex;
 	U32 mFBO;
+	U32 mColorFmt;
 	U32 mDepth;
 	BOOL mStencil;
 	BOOL mUseDepth;
 	BOOL mRenderDepth;
+
 	LLTexUnit::eTextureType mUsage;
 	U32 mSamples;
 	LLMultisampleBuffer* mSampleBuffer;