Maybe for @cuinjune ...?

As part of my continuing quest to figure out how to work with pixel data in Ofelia, I was looking into shaders this weekend. (I don't understand why this has to be a quest, but... there we are.)

I've tried multiple permutations cobbled together from various examples, but I can't successfully get the texture coordinates into the shader.

I'm perplexed. I tried copying a simple texture example from https://riptutorial.com/opengl/example/32426/using-textures-in-glsl-shaders:

in vec2 texCoordOut;

out vec4 color;

uniform sampler2D image;

void main()
{
    color = texture(image, texCoordOut);
}

But this crashes Ofelia upon shader:load(...). (Don't even have to beginShader() -- just dies on init.)

OK, so then I copied a fragment shader out of Ofelia's own examples:

uniform sampler2DRect tex0;             

varying vec2 texCoordVarying;

void main()
{
    gl_FragColor = texture2DRect(tex0, texCoordVarying);
}

... and... "ofShader: ofShader: program reports: error: fragment shader input `texCoordVarying' has no matching output in the previous stage."

Or

uniform sampler2DRect tex0;             

// varying vec2 texCoordVarying;
in vec2 coord;

void main()
{
    gl_FragColor = texture2DRect(tex0, coord);
}

No crash, but "error: 'in' qualifier in declaration of 'coord' only valid for function parameters in GLSL 1.10"

Sooooooo... sorry for being an idiot about this. I need pixel manipulations for a course. AFAICS shaders should be able to do this, and based on online reading, it doesn't make sense to me that it's this blastedly difficult.

hjh

@Jona said:

u can even declare which version to use (and there is a default version enabled):
"ofelia's ofWindow() class uses openGL 2.1 as a default and you can change the GL version before you create a window like the following:

Ok, great!

The end goal of all this is to create some abstractions for common pix operations (perhaps add to 60hz's library), so that users can do some basic stuff (gain, levels, alpha masking) without all users having to go down this rabbit hole individually -- and also maybe serve as a template for others to implement more pix ops in the future. So portability is a big concern.

Thanks for the tips -- I was getting very confused.

hjh

Nope. I'm trying everything. My image is not black. texture2DRect returns only black. The Lua script is binding the image but the shader cannot see anything other than black.

#version 120

uniform sampler2DRect tex0;  // also tried Tex0

void main()
{
    vec2 res = vec2(100.0, 100.0);
    vec2 pos = gl_FragCoord.xy / res.xy;
    vec4 color = texture2DRect(tex0, pos);  // also tried Tex0
    gl_FragColor = color;  // this is always black. Why is this always black...?
    // so I know gl_FragCoord.xy is changing
    // gl_FragColor = vec4(pos.x, pos.y, 1.0, 1.0);
}

The commented bit works btw... so I'm quite sure it's only the texture2DRect call that is doing nothing.

hjh

@ddw_music try sampler2D instead.

@Jona said:

@ddw_music try sampler2D instead.

I could swear I had tried that yesterday and it crashed Pd.

But today... yeah, that's the thing. Thanks a million for the tips. I was near to giving up.

That is the hardest learning curve I've ever encountered, in any kind of software. Sheesh. (There really needs to be a meta-language for this.)

In case anyone else runs into the same trouble, here's the working Lua script and 2 shader files:

script.lua:

if type(window) ~= "userdata" then;
window = ofWindow();
end;
;
local canvas = ofCanvas(this);
local shaderDir = canvas:getDir() .. "/";
local shader = ofShader();
local img = ofImage();
local useShader = 0;
local gradient = 0;
;
function M.new();
ofWindow.addListener("setup", this);
ofWindow.addListener("draw", this);
ofWindow.addListener("exit", this);
window:setPosition(0, 0);
window:setSize(100, 100);
if ofWindow.exists then;
clock:delay(0);
else;
window:create();
end;
end;
;
function M.free();
window:destroy();
ofWindow.removeListener("setup", this);
ofWindow.removeListener("draw", this);
ofWindow.removeListener("exit", this);
end;
;
function M.setup();
ofSetWindowTitle("shader1");
ofBackground(255, 255, 255, 255);
img:allocate(10, 10, OF_IMAGE_COLOR);
for i = 0, 99, 1 do
color = ofColor(i);
img:setColor(i * 3, color);
end;
img:update();
M.pln = ofPlanePrimitive();
M.pln:setRows(4);
M.pln:setColumns(4);
M.pln:setWidth(100);
M.pln:setHeight(100);
M.pln:setPosition(ofVec3f(50.0, 50.0, 0.0):vec3());
shader:load(shaderDir .. "gain");
end;
;
function M.useShader(f);
useShader = f;
end;
;
function M.gradient(f);
gradient = f;
end;
;
function M.draw();
ofSetColor(255);
img:bind();
if(useShader ~= 0) then shader:beginShader() end;
shader:setUniform1f("gradient", gradient);
M.pln:draw();
if(useShader ~= 0) then shader:endShader() end;
img:unbind();
end;
;
function M.exit();
shader:unload();
img:clear();
end

gain.vert:

#version 120

void main()
{
    gl_Position = ftransform();
}

gain.frag:

#version 120

uniform sampler2D tex0;
uniform float gradient;

void main()
{
    vec2 res = vec2(100.0, 100.0);
    vec2 pos = gl_FragCoord.xy / res.xy;
    if(gradient != 0.0) {
        gl_FragColor = vec4(pos.x, pos.y, 1.0, 1.0);
    } else {
        vec4 color = texture2D(tex0, pos.xy);
        if(gl_FragCoord.xy.x > 50.0) { 0; } else {
            color.r = color.r * 2.0;
        };
        gl_FragColor = color;
    }
}

hjh

@ddw_music
actually your vertex shader also works with my patch (and looks much simpler than what i was using)...

@ddw_music
"to create some abstractions for common pix operations (perhaps add to 60hz's library), so that users can do some basic stuff (gain, levels, alpha masking) without all users having to go down this rabbit hole individually -- and also maybe serve as a template for others to implement more pix ops in the future"...
i already made / adapted a collection of basic shaders, most of them can be optimized and written in a more standard way, but perhaps they are helpful for a start:
https://forum.pdpatchrepo.info/topic/12152/ofelia-glsl-video-effects
https://forum.pdpatchrepo.info/topic/12141/ofelia-glsl-shader-loader/13

@Jona said:

i already made / adapted a collection of basic shaders, most of them can be optimized and written in a more standard way, but perhaps they are helpful for a start:
https://forum.pdpatchrepo.info/topic/12152/ofelia-glsl-video-effects
https://forum.pdpatchrepo.info/topic/12141/ofelia-glsl-shader-loader/13

Hmm, yes, that will be helpful. It remains to work out how to integrate these ideas into 60hz's system. (I still need to look over his recent idea about passing image IDs through.)

It looks like the chain will have to go like image --> shader renders to fbo --> get the texture to use for mapping onto a (possibly transformed) geo. I'm not sure what happens if the user stuck a transformation in before the shader though... have to try later. It's either that the fbo is independent of a transformation, or it's subject to previous transformations. Or maybe just draw the image onto the fbo...? Didn't get that far yet.

hjh

Now I'm finding that the texture is going white at intermittent times... any guesses? The only way to fix it is to reload the image object. The shader shouldn't be affecting the image buffer.

hjh