RT @djcoreynolan: Ahh so now I know what @Lumin0via and I would look like if we were assimilated into the @kylepulver universe. <3 t… (Yesterday)

@ComcastMike Oh, no, that would be @goldbuick! (Yesterday)

@chickysprout @dom2d waaaaaa this looks fucking fantastic! STYLIN'~ (Yesterday)

@goldbuick @comcast Yeah it's amazing how progress somehow totally reversed at some point. Bandwidth caps are ancient. (Yesterday)

@goldbuick @comcast Holy shit that's insane. I didn't think companies actually charged for more bandwidth in the US. (Yesterday)

@SteveSwink @MattThorson yooooooooooooooooooooo were you able to fix the shoulder button squish? (Yesterday)

@infinite_ammo David haven't you been watching?! DAVID. (Yesterday)

@ThemsAllTook Auugh I cant stand it. I always feel like I'm the most terrified person on the whole flight. (Yesterday)

Smooth flight: Wow flying is so cool I should do this more. Bumpy flight: FUCK THIS I AM NEVER FLYING AGAIN FUCK (2 days ago)

@notch @TommyRefenes "WOW THIS IS GOING TO BE GREAT I KNOW EXACTLY WHAT TO DO" *sit down at computer* "I have no idea what to do." (3 days ago)

@ChevyRay Silviu Stan strikes again. (3 days ago)

RT @Capy_Nathan: Every year @RichhhardLi puts out beautiful, intense, emotional videos from EVO. This year's is just phenomenal. t.… (3 days ago)

@TommyRefenes YEAH John Hammond was able to place a copyright strike on the painting after google bought it :( (3 days ago)

@Marshall2Re hey thanks! ;D (3 days ago)

Anonymous inside sources confirmed that Google has purchased a pretty cool painting of a Stegosaurus at a yard sale for 0.000000001 billion (3 days ago)

@TommyRefenes dang you got like 9999 pills (3 days ago)

@Livelyivy Oh nooooo I thought we sealed off the murder hole once and for all (4 days ago)

@fncwill I wasn't playing, only saw the screen. (4 days ago)

Nobody is a loser at the Saratoga Casino and Raceway! (You could be a "looser" though.) t.co/b6HOTas7eR (4 days ago)

@PuppyWarrior @MattThorson When the only thing that the reviews mention is the addiction, and it's a mobile game, I don't have high hopes. (4 days ago)

follow
search

2014 - 6 - 10 / 7:48 pm / general

Dev Log: Shaders All Day

Dev Log: Shaders All Day

I've been taking an extended vacation in shader town lately, and so far I've been having a lot of fun! One of the things I was figuring out was how to take an image and remap all the colors to a gradient based on their luminosity (well, a sloppy way of estimating the luminosity.) This seems like a pretty powerful effect that could be used to really spice up effects. Yeah, I'm always thinking about how to make explosions better.

First I'll share the actual shader code that I'm working with right now. This is the shader that's being used for all of my full screen effects.

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

void main() {
vec4 displacementPixel = texture2D(displacementMap, gl_TexCoord[0]);
vec4 palettePixel = texture2D(paletteMap, gl_TexCoord[0]);

vec2 pos = gl_TexCoord[0];
pos.x += (displacementPixel.r * 2.0 - 1.0) * 0.025 * displacementPixel.a;
pos.y -= (displacementPixel.g * 2.0 - 1.0) * 0.025 * displacementPixel.a;

// 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);

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);

gl_FragColor = pixel * gl_Color;
}

Using Otter I can just apply this shader to the game's main Surface object and I'm ready to roll with special effects. This post is going to be image heavy, so I'll hide the rest of it behind the jump!

This shader is handling two major special effects. One is a displacement effect which can be used for ripples, shockwaves, and other neat effects like a stained glass look. The other effect is a gradient map mask effect which allows me to specify parts of the screen that have their colors remapped to a specified palette.

Both of these effects make use of a behind-the-scenes Surface in Otter. I can draw graphics directly to these hidden surfaces and then pass them into the shader via a texture parameter. Then I can use the color data from the sampled pixels in the shader.

Displacement
The displacement effect uses pixel data to determine the amount of displacement. A red pixel on the displacement texture will move a pixel horizontally on the game's surface depending on how red it is. A green pixel will do the same thing but vertically. Since this is 2D displacement, blue doesn't do anything. The alpha of the pixel also determines how much of an offset there is in the displacement.

This allows me to do stuff like this,

Image

In that example the texture that was used for the displacement is a random normal map sample that I grabbed off of Google.

Image

That's just a static example. What happens if when I use a Surface to pass in a texture that is being drawn on dynamically? Then I can do stuff like this,

Image

Image

You can see some wave like effects around the explosions now. I haven't quite figured out how to get a proper looking shockwave coming out of the center of the explosion yet though... so for now you get to see wobbling of space time.

Gradient Maps
Gradient maps are awesome and I love using them in Photoshop, so I've been really excited to get them working with shaders. Basically what I'm looking to do is take colors on the screen and remap them to new colors from a gradient texture. Here's a quick look at a gradient texture I'm using for some experiments right now.

Image

It's pretty easy to get a gradient map working on an entire texture, but what I really wanted to look into was doing gradient maps on only specific parts of the screen. Using what I learned with displacement maps, I wanted to apply the same concepts.

I'm using a different Surface in Otter. I'm rendering images to that surface and passing the texture data to the shader. The shader then looks at the pixels of that surface to figure out what to do in regards to the gradient remap.

First the shader figures out how "gray" the pixel is. Then that determines what color on the gradient to use. Since the gray is 0 to 1, I can just get the pixel off of the gradient that horizontally maps to that. For example, if the gray is 0, then I sample the left most pixel of the gradient (usually the darkest color.) If the gray is 1, I sample the right most, and 0.5 is right in the middle.

I also use the green pixel data from the palette mapping surface to determine an offset for the horizontal position of the gradient. I figure this can be used for some pretty cool effects if I can cycle the gradient over an image.

To determine which part of the gradient to use I sample the red pixel on the palette mapping surface. This is why my gradient image is actually a square and not just a horizontal strip. The red pixel will determine the vertical position on that image to sample, so I can use many different gradients just coming from one texture depending on how red the sampled pixel is.

Enough babbling about that, check out this sort-of accidental effect that I was experimenting with,

Image

Pretty rad! Although as you can see right now the hud is also caught up in the madness of the displacements and the color mapping. I'll fix this later by placing the hud on a different surface that wont be effected by shaders.

That's all for now!

6 Comments
Avatar

2014 - 6 - 10 10:18 PM

Oliver

Damn, those explosions and shock waves. :3

Avatar

2014 - 6 - 10 10:33 PM

A333

Such juicy explosions, i could blow the stuff up all day like that. Great result.

> I'll fix this later by placing the hud on a different surface that wont be effected by shaders.

Or maybe you shouldn't. It really adds to the immersion =)

Avatar

2014 - 6 - 10 11:34 PM

Michi

Ahh, cool stuff with the gradient map, that sort of thing might come handy sometime! Thanks!

Avatar

2014 - 6 - 10 11:39 PM

Kyle

Thanks everyone :3

A333: for the hud it really depends on how crazy I go. If the hud is still readable enough I'll keep the effects on it. ;D

Avatar

2014 - 6 - 11 6:46 AM

Abel Toy

It would be interesting to see the distortion mask and the gradient mask as well, to see how are you making the effect behind the scenes!

Avatar

2014 - 6 - 11 1:57 PM

Kyle

Yeah, I think I'll do another post with the masks and the result.

Avatar

Post your comment!

POST COMMENT

about

About

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.

facebook

videos

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!

contact

Your message has been sent! Thanks :)
SEND MESSAGE