XNA4 - Trouble updating part of a Texture2D

Question

I have a big Color[] ColorMap in memory (1280x720), and I have a Texture2D that I've uploaded this ColorMap to. I update parts of the in-memory ColorMap, and want to upload those changed parts to the texture. I'd rather not reupload the entire texture every time, so I'd like to use

public void SetData<T> (
     int level,
     Nullable<Rectangle> rect,
     T[] data,
     int startIndex,
     int elementCount
) 

As far as I can see, I can not use this directly to upload just a part of my in-memory map to the texture since I can't specify a stride in the SetData method.

So say I'd like to update the area specified by DirtyRect, i'd first need to create a temporary in-memory buffer

Color[] tempBuffer = new Color[DirtyRect.Width*DirtyRect.Height];

then copy the wanted data from my ColorMap to the tempBuffer, and then upload the tempBuffer to my Texture2D like

Text.SetData<Color>(0, DirtyRect, tempBuffer, 0, DirtyRect.Width*DirtyRect.Height);

This seems to work - sometimes... But sometimes it appears in the wrong place ?!

If I get rid of the rectangle code and reupload the entire texture every time using

Tex.SetData(ColorMap);

it works fine, so apparently I must be doing something wrong.

Anyone got any idea ? Or is there any code-example of updating only parts of a texture that I can have a look at (XNA 4) ?

Cheers.

Answer 1

Never mind, I'll just go stand in the corner with my stupid-hat on :-/

There's nothing wrong with the SetData methods, I accidentally swapped a "point.X" with a "point.Y" in some code that would execute only very rarely. That it only showed up when I was using the SetData without rectangle was pure coincidence.

But one question remains - why do i need to copy part of my big ColorMap into a smaller version before I can upload the partial bit ? That's extremely inefficient ! Why isn't there a version where I can specify an array and a stride so I can copy straight from the source ?