Request: backbuffer sample

[DinhQuocTrung]

Could you add a basic sample about backbuffer to store and load data to use later? May be store data on only one pixel?
I have seen game of life sample, I thing that you could add a sample like using mouse to change color.
It will be very useful for beginners.
Thank you.

[anmolshowcase]

I Agree, it would be great if we could save one pixel data in memory and modify it when needed. backbuffer works great until you need to sample the last frame but in my case i want to sample how much time has passed since the last touch was performed and if i could store the time data in a pixel value and reference it in next frame it would work. :)

I hope we get something like that soon.

[AntonPieper]

I think what you really want would be the ability to also write scripts for the CPU as well.

This would require the addition of an actual filesystem and a scripting language like LuaJ or JavascriptEngine. JavascriptEngine would require API level 26 though.

Custom variables

Custom variables could be passed using a setUniform API and the data can be modified in the main loop.

Script Examples for Lua/JavaScript

Lua Custom Variables

local engine = require("ShaderEngine")

-- Create a shader object
local shader = engine:createShader("./main.glsl")

-- Initialize sensors
local accelerometer = engine:initProvider("accelerometer")

local myCustomData = vec2.new(0, 0)

-- Function to update uniforms
local function updateUniforms(shader)
    -- Pass sensor data to the shader as uniforms
    shader:setUniform("accelerometer", accelerometer:getData())
    shader:setUniform("myCustomData", myCustomData)
    shader:setUniform("backbuffer", engine:getBackBufferTexture())

    local time = engine:getTime()

    shader:setUniform("time", time)

    myCustomData:add(1, 0)
end

-- Start the engine loop
while engine:running() do
    -- Clear the screen
    engine:clear()

    -- Update sensors
    accelerometer:update()

    -- Update shader uniforms
    updateUniforms(shader)

    -- Render the full-screen shader
    engine:render{ shader = shader }

    -- Swap buffers to display the rendered frame
    engine:swapBuffers()
end

JavaScript Custom Variables

import engine from "shader-engine";

// Create a shader object
const shader = engine.createShader("./main.glsl");

// Initialize sensors
const accelerometer = engine.initProvider("accelerometer");

const myCustomData = new Vec2(0, 0);

// Function to update uniforms
function updateUniforms(shader) {
    // Pass sensor data to the shader as uniforms
    shader.setUniform("accelerometer", accelerometer.data);
    shader.setUniform("myCustomData", myCustomData);
    shader.setUniform("backbuffer", engine.backBufferTexture);

    const time = engine.time;

    shader.setUniform("time", time);

    myCustomData.add(1, 0);
}

// Start the engine loop
while (engine.running) {
    // Clear the screen
    engine.clear();

    // Update sensors
    accelerometer.update();

    // Update shader uniforms
    updateUniforms(shader);

    // Render the full-screen shader
    engine.render({shader});

    // Swap buffers to display the rendered frame
    engine.swapBuffers();
}

Default Script

To not break backwards compatibility, a default script could be used and all shaders get converted into a {shader_name}/main.glsl path.

Script Examples for Lua/JavaScript

Lua Default Script

local engine = require("ShaderEngine")
local shader = engine:createShader("./main.glsl")
local sensors = engine:initProviders(shader:getUniformNames())

while engine:running() do
    engine:clear()
    for k, v in pairs(sensors) do
        v:update()
        shader:setUniform(k, v:getData())
    end
    engine:render{ shader = shader }
    engine:swapBuffers()
end

JavaScript Default Script

import engine from "shader-engine";

const shader = engine.createShader("./main.glsl");
const sensors = engine.initProviders(shader.uniformNames);

while (engine.running) {
    engine.clear();
    for (const [key, value] of Object.entries(sensors)) {
        value.update();
        shader:setUniform(key, value.data);
    }
    engine.render({shader});
    engine.swapBuffers();
}