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    Modify Texture

    wefewefe Member
    in General questions
    Hello

    First: I'm new to this forum, and my english is not very good. Sorry about.

    My problem is. I want to write a small retro game and stuck with texture modify.

    I want a texture from the size 256x256 and modify parts of it every frame.


    My first thought:

    local tex = Texture.new( "images/test.png", false )
    local bm = Bitmap.new( tex )

    One time "Texture.new", and then each frame delete bitmap and recreate it.
    The texture is stored in CPU memory and the bitmap in GPU memory, right?

    But how can I have access to the pixel data from the texture?


    My other thought:

    local size = 256
    local stringbm = string.rep( string.char( 255,255,0,255 ), size*size )
    local tex = Texture.new( stringbm, size, size, false, {} )
    local bm = Bitmap.new( tex )

    This try stores the texture data in a string. And I want to delete the bitmap and texture every frame, modify the stringbitmap, and then recreate it.
    But I cannot modify the string in Lua...


    Have anyone a good problem solving for me?

    Likes: antix

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    Comments

    • rrraptorrrraptor Member
      Accepted Answer
      Use RenderTarget
      local random=math.random
local w,h = 256,256
local rt = RenderTarget.new(w,h)
local btm = Bitmap.new(rt)
stage:addChild(btm)
 
for y = 1, h do 
	for x = 1, w do 
		rt:clear(random(0xffffff),1,x,y,1,1) -- can be read as setPixel with random color at x,y
	end
end

      Likes: keszegh

      SuperShape | Nice blured shapes with shadows | Simple button pad | Simple layer class | Simple UI library | 2D camera lib | Color picker | FPS graph | Dear ImGui | cute_c2
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    • keszeghkeszegh Member
      btw i think that the texture is stored in gpu memory if it fits. and the bitmap is not storing it again, just a pointer to it, or something like this. so my guess would be that 100 bitmaps with same texture do not need much more memory than 1 bitmap with one texture. am i right, experts?
      Longtitle Productions, creator of
      Fragmenter - animated loop machine and IKONOMIKON - the memory game
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    • wefewefe Member
      RenderTarget is a very good solution!
      I didn't think in that direction at all.

      When texture and bitmap are stored in GPU memory. Then it is clear why it is not so easy to read.

      Thank you very much!
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    • hgy29hgy29 Maintainer
      keszegh said:

      btw i think that the texture is stored in gpu memory if it fits. and the bitmap is not storing it again, just a pointer to it, or something like this. so my guess would be that 100 bitmaps with same texture do not need much more memory than 1 bitmap with one texture. am i right, experts?

      Totally right, the bitmap holds the mesh only, the texture is stored independently and referenced by any other sprite that use it

      Likes: keszegh

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