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2014 - 6 - 2 / 4:09 pm / general

Dev Log: Shader Experiments

Dev Log: Shader Experiments

Since my break to work on the remaining bits of Otter I haven't really fallen back into the groove on working on my big game project yet. Yesterday I dedicated the day to playing around with shaders since I'm really interested in using them for all kinds of cool visual effects.

Image

This is what I ended up coming up with at the end of the day. First I was playing around with gradient maps for recoloring an image, and then I started to mess with displacement to make cool waves in the image. Finally I wanted to experiment with having a render texture that could be passed to the shader for dynamic effects.

Basically how this little program works is that there is the static image with a shader loaded. Then there's a Surface object that can be painted on with the mouse. The shader uses the texture from that Surface to affect the image in different ways.

Here's the full C# source:

using Otter;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ShaderTesting {
class Program {
static void Main(string[] args) {
var image = new Image("pic.jpg");
var game = new Game("ShaderZ", image.Width, image.Height);

game.FirstScene = new TestScene();

game.Start();
}
}

class TestScene : Scene {

Image image = new Image("pic.jpg");
Image circle = new Image("circle.png");
Surface distortion;

public TestScene() {
AddGraphic(image);
distortion = new Surface(image.Width, image.Height);
circle.CenterOrigin();
circle.Blend = BlendMode.Add;
AddGraphic(distortion);
circle.Alpha = 0.1f;
distortion.Visible = false;
distortion.AutoClear = false;
}

public override void Update() {
base.Update();

if (Timer % 30 == 0) {
try {
image.Shader = new Shader("../../shader.frag");
}
catch(Exception e) {
Console.WriteLine("Shader error:");
Console.WriteLine(e.Message);
}
image.Shader.SetParameter("gradient", new Texture("gradient.png"));
}
if (Input.MouseButtonPressed(MouseButton.Right)) {
distortion.Clear();
}
image.Shader.SetParameter("time", Timer);
image.Shader.SetParameter("distortion", distortion.Texture);
image.Shader.SetParameter("offset", Util.SinScale(Timer, 0, 1));

if (Input.MouseButtonDown(MouseButton.Left)) {
Draw.SetTarget(distortion);
Draw.Graphic(circle, MouseX, image.Height - MouseY);
Draw.ResetTarget();
}
}

public override void Render() {
base.Render();

Draw.Circle(MouseX - 15, MouseY - 15, 30, Color.None, Color.Red, 2);
}
}
}


And the GLSL shader source:

sampler2D texture;
sampler2D gradient;
sampler2D distortion;
uniform float offset;
uniform float time;
uniform float mixfactor;

void main() {
vec2 pos = gl_TexCoord[0];
vec2 distortColor = texture2D(distortion, pos);
pos.x += distortColor.r * (sin(time * 0.1 + pos.x * 10) * 0.05);
pos.y -= distortColor.g * (cos(time * 0.1 + pos.y * 10) * 0.05);
vec4 color = texture2D(texture, pos);

float gray = (color.r + color.g + color.b) / 3;

vec4 gradientColor = texture2D(gradient, vec2(gray, offset));

gl_FragColor = mix(color, gradientColor, distortColor.r + distortColor.g);
}


You can download everything here. Note that you'll have to give it a reference to Otter to compile and run it yourself.

2 Comments
Avatar

2014 - 6 - 10 9:57 PM

R Brack

Are you meant to be creating a new shader and texture every 30 (seconds? milliseconds?) That seems a bit rough to me.

Avatar

2014 - 6 - 11 1:25 AM

Kyle

It's actually every half second (60 fps.) It's so I can edit the shader, save, and see my changes almost instantly instead of having to rebuild the application. I don't notice any performance issues.

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Hi there, my name is Kyle, and I'm a 27 year old kid with adult powers. I'm making video games and living the indie game developer life in Tempe, Arizona. Here you will find my thoughts, games, websites, doodles, and other stuff like that. I worked on Snapshot, Offspring Fling, and a whole bunch of other games. I also created and maintain Otter, a 2d game making framework. If you want to get a hold of me use the form on the bottom of the page, leave a comment, or just tweet at me. I try to post three times a week. Thanks for stoppin' by! You're the coolest.

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