@phubans @tylerglaiel @SteveSwink @djcoreynolan this is my favorite video game movement ever (Today)

@rabbit_nabokov I can send you a build if you want but I no longer appear on skype (Yesterday)

A fierce battle and a cool battle log graph from Super Sky Sisters for #screenshotsaturday Almost done! :B t.co/1uZZFFCXXK (Yesterday)

@MANvsGAME at least it's sorted into stacks (2 days ago)

@Capn_Andy @ColinNorthway I agree with Colin here. (4 days ago)

My favorite internet radio station to work to has returned again! t.co/GHuSllopkU (4 days ago)

@benprunty ben prunty goa psytrance yes yes (4 days ago)

@rice_cooky @rabbit_nabokov a m a z i n g (4 days ago)

@MoviusC yeah I guess I wore pants at the time, this was years ago, hard to remember for an old man such as myself. (4 days ago)

@Krynis @spacecoyotl @theyetee I think the yetee now claims over 50% of my t shirt collection haha (4 days ago)

@MoviusC In my youth video game shirts were so hard to come by. My entire wardrobe at one point though was Dragonball Z shirts though. (4 days ago)

@messofanego If I were a kid that couldn't afford most games I would totally be watching LPs all the time, it makes sense. (4 days ago)

RT @Lumin0via: @kylepulver I'M SORRY D: (4 days ago)

@Lumin0via hahahah <3 (4 days ago)

I recently asked a young whippersnapper if they had more "lets players" shirts than video game shirts. They said yes and my mind melted. (4 days ago)

RT @rabbit_nabokov: please consider helping the development of Momodora 4: t.co/3v5CY8vcOK just spreading the word helps a lot! htt… (4 days ago)

@Capn_Andy Gibson status: hacked. (7 days ago)

@AsherVo yeah whatever let me know when it can make a driverless car pick you up and go off a sweet jump on top of a parking garage (9 days ago)

@jethrolarson hahah why would they allow comments on Ted talks that's just a recipe for disaster (10 days ago)

Are there any GDC talks along the lines of "how to make cool stuff without being crippled by self doubt and overwhelming anxiety" ?? (10 days ago)


2014 - 6 - 11 / 4:06 pm / general

Dev Log: Shader Follow Up

Dev Log: Shader Follow Up

My last post went over some of my recent shader developments with displacement maps, and using gradient maps to recolor portions of the screen. I had a couple of questions of what exactly was going on behind the scenes with the render textures that I was using to tell the shader how to actually manipulate the image, so I thought I would address that now!

Here's an example image from the game with a lot of explosions going on:


Each explosion has a shockwave ripple coming out of it which distorts the area around it. The explosion also changes the color of the screen around to a gradient map with pink and yellow. This makes it look like an intense heat, or something.

For reference, here's the shader again (it's been slightly modified since yesterday.)

uniform sampler2D texture;
uniform sampler2D displacementMap;
uniform sampler2D paletteMap;
uniform sampler2D gradientMap;

void main() {
// Get the pixels off of the maps.
vec4 displacementPixel = texture2D(displacementMap, gl_TexCoord[0]);
vec4 palettePixel = texture2D(paletteMap, gl_TexCoord[0]);

// Read the pixel from the displaced position.
vec2 pos = gl_TexCoord[0];
pos.x += (displacementPixel.r * 2.0 - 1.0) * 0.025;
pos.y -= (displacementPixel.g * 2.0 - 1.0) * 0.025;

// Get the displaced pixel.
vec4 pixel = texture2D(texture, pos);

// Proper grayscale conversion.
float gray = dot(pixel.rgb, vec3(0.299, 0.587, 0.114));

// Get the color from the gradient.
float gradientPos = mod(gray + palettePixel.g, 1);

// Get the actual color from the gradient.
vec4 gradientMapPixel = texture2D(gradientMap, new vec2(gradientPos, palettePixel.r));

// Mix the gradient with the pixel color based on the palette pixel.
pixel = mix(pixel, gradientMapPixel, palettePixel.a);

// Apply the final color multiplied by the gl color.
gl_FragColor = pixel * gl_Color;

From this point on there's going to be a lot of images and some hefty animated gifs, so I'll hide the rest of this post behind the read more button!

Now here's what the displacement map actually looks like:


And here's the image that I'm using to get the shockwave displacement:


The displacement map is filled with gray (127, 127, 127) each frame, and then that shockwave image is rendered to it, much like how each frame for the game window is cleared and then rendered to with many different graphics. After the displacement map has been rendered to, I pass its texture to the shader to use for the displacement.

The gradient mapping is a little simpler. The explosions just render a blue glow to the surface that determines how to remap the colors. Here's how that looks behind the scenes:


And now when it all comes together!


And of course here's a quick look at the shock wave animating:



2014 - 6 - 12 4:57 AM

Abel Toy


I'm amazed at what you can do with shaders, really. That effect is so powerful, and with a really small ammount of code.

I can't wait to experiment with shaders as well, cause that looks fantastic.

Thanks for sharing this insightful post, great job! Can't wait to play with your game :)


2014 - 6 - 22 6:50 AM


This looks really rad makes my tummy go crazy :')


2014 - 6 - 22 12:38 PM


Thanks! :)


2014 - 9 - 10 1:46 PM


That's really amazing.
I wanted to play around with that shader a little bit, so I ported it over to HLSL. I found that the line where you mod the u pos to get the gradientPos was creating artifacts, because it causes the u value to jump to 0 when reaching 1 (which results in jumping from an onscreen white to black on the gradient map). When I removed the line the effect was working a lot better.

Is it cool if I steal the idea with the gradient map for my own projects? :D


2014 - 9 - 11 2:54 PM


Oh weird about the mod issue! Maybe that is a difference with how mod works on HLSL? I don't think I've noticed this on my experiements so far.

Feel free to "steal" the technique! I posted it so that hopefully people would use it on their own stuff ;)


Post your comment!




Hi there, my name is Kyle, and I'm a kid disguised as a grown up. 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.



Do you want to make a Let's Play of one of my games, or a just a video featuring footage of my games? You have my full permission to do so! Even if you are monetizing your videos, you still have my full permission to use any footage from any of my games. Go for it!


Your message has been sent! Thanks :)