Drawing a section of a 2D texture (Setting UV coords)

[Ruki]

Hi, I recently upgrading from LE2 to LE3. I'd like to draw a section of a texture directly onto the screen for my GUI. My GUI texture contains lots of elements that I need to draw individually. I achieved this in LE2 using an OpenGL extension where I could set vertices and their texture coordinates, but I can't access OpenGL with LE3 can I? I'm using Context->DrawImage(...) but it has no parameters for texture UV.. So how do I do this? With a shader? I've never used shaders before so I'm completely baffled by them :| Please help! Thank you

[gamecreator]

Shadmar can do miracles with shaders and I think he helped someone in the last few months with them so I'd search the forums. But the other option is to copy texture pixels yourself.

http://www.leadwerks.com/werkspace/page/documentation/_/command-reference/texture/texturesetpixels-r338

The examples are down at the moment and oddly this is one of the functions that can really use it. Hope they come back soon.

[macklebee]

If you are using c++, I believe you can still use opengl commands. Or you can do it via a shader.

 

Unzip and place this shader in your project's 'Shaders/Drawing' folder:

drawimageparts.zip

 

To Use:

• shader = Shader:Load("Shaders/Drawing/drawimageparts.shader")
  
• shader:SetVec2("uvcoords", Vec2(#,#))
  
• shader:SetVec2("zoom", Vec2(#,#))
  
• oldshader = context:GetShader()
  
• context:SetShader(shader)
  
• context:DrawImage(LoadedImageToDraw, x , y, w, h)
  
• context:SetShader(oldshader)
  

 

 

Example code showing usage:

function App:Start()

self.window = Window:Create("Part of Image Example",0,0,800,600)

self.context = Context:Create(self.window)

self.world = World:Create()

self.camera = Camera:Create()

self.texture = Texture:Load("Materials/Developer/bluegrid.tex")

self.shader = Shader:Load("Shaders/Drawing/drawimageparts.shader")--load shader

uvcoords = 1.0

zoom = 2.0

return true

end

 

function App:Loop()

if (self.window:Closed() or self.window:KeyDown(Key.Escape)) then return false end

 

uvcoords = uvcoords + ((self.window:KeyHit(Key.Up) and 1 or 0) - (self.window:KeyHit(Key.Down) and 1 or 0)) * 0.1

zoom = zoom + ((self.window:KeyHit(Key.Right) and 1 or 0) - (self.window:KeyHit(Key.Left) and 1 or 0)) * 0.1

self.shader:SetVec2("uvcoords", Vec2(uvcoords))--set uvcoords in shader

self.shader:SetVec2("zoom", Vec2(zoom))--set zoom in shader

 

Time:Update()

self.world:Update()

self.world:Render()

 

self.oldshader = self.context:GetShader()--get current shader

self.context:SetBlendMode(Blend.Alpha)

self.context:SetShader(self.shader)--set new shader

self.context:DrawImage(self.texture,405,150,300,300)--clipped/scaled image

self.context:SetShader(self.oldshader)--set back to previous shader

 

self.context:DrawImage(self.texture,100,150,300,300)--normal drawimage

self.context:DrawText("Press Up/Down to change uvcoords", 0, 2)

self.context:DrawText("UVCoords: "..uvcoords..", "..uvcoords, 0, 22)

self.context:DrawText("Press Right/Left to change zoom", 0, 42)

self.context:DrawText("Zoom: "..zoom..", "..zoom, 0, 62)

self.context:SetBlendMode(Blend.Solid)

self.context:Sync();

return true

end