diff options
Diffstat (limited to 'content')
| -rw-r--r-- | content/blog/blacklight_shader/blacklight.png | bin | 846587 -> 0 bytes | |||
| -rw-r--r-- | content/blog/blacklight_shader/index.md | 171 | ||||
| -rw-r--r-- | content/projects/nix_aurea/index.md | 11 |
3 files changed, 0 insertions, 182 deletions
diff --git a/content/blog/blacklight_shader/blacklight.png b/content/blog/blacklight_shader/blacklight.png Binary files differdeleted file mode 100644 index 2c5caf1..0000000 --- a/content/blog/blacklight_shader/blacklight.png +++ /dev/null diff --git a/content/blog/blacklight_shader/index.md b/content/blog/blacklight_shader/index.md deleted file mode 100644 index c5e4b27..0000000 --- a/content/blog/blacklight_shader/index.md +++ /dev/null @@ -1,171 +0,0 @@ -+++ -title = "creating a blacklight shader" -date = 2024-11-29 -[taxonomies] -projects = ["bevy_blacklight_material"] -+++ - -today i wanted to take a bit of time to write about a shader i implemented for my in-progress game project (more on that soon™) - -i wanted to create a "blacklight" effect, where specific lights could reveal part of the base texture. this shader works with **spot lights** only, but could be extended to work with point lights - -; - -i wrote this shader in wgsl for a [bevy engine](https://bevyengine.org) project, but it should translate easily to other shading languages - -the finished shader can be found as part of [this repo](https://github.com/soaosdev/bevy_blacklight_material) -## shader inputs - -for this shader, i wanted the following features: -- the number of lights should be dynamic -- the revealed portion of the object should match the area illuminated by each light - - the falloff of the light over distance should match the fading of the object - -for this to work i need the following information about each light: -- position (world space) -- direction (world space) -- range -- inner and outer angle - - these will control the falloff of the light at its edges - - outer angle should be less than pi/2 radians - - inner angle should be less than the outer angle - -i also need some info from the vertex shader: -- position (**world space!**) -- uv - -bevy's default pbr vertex shader provides this information, but as long as you can get this info into your fragment shader you should be good to go - -lastly i'll take a base color texture and a sampler - -with all of that, i can start off the shader by setting up the inputs and fragment entry point: - -```wgsl -#import bevy_pbr::forward_io::VertexOutput; - -struct BlackLight { - position: vec3<f32>, - direction: vec3<f32>, - range: f32, - inner_angle: f32, - outer_angle: f32, -} - -@group(2) @binding(0) var<storage> lights: array<BlackLight>; -@group(2) @binding(1) var base_texture: texture_2d<f32>; -@group(2) @binding(2) var base_sampler: sampler; - -@fragment -fn fragment( - in: VertexOutput, -) -> @location(0) vec4<f32> { -} -``` -(bevy uses group 2 for custom shader bindings) - -since the number of lights is dynamic, i use a [storage buffer](https://google.github.io/tour-of-wgsl/types/arrays/runtime-sized-arrays/) to store that information - -## shader calculations - -the first thing we'll need to know is how close to looking at the fragment the light source is - -we can get this information using some interesting math: - -```wgsl -let light = lights[0]; -let light_to_fragment_direction = normalize(in.world_position.xyz - light.position); -let light_to_fragment_angle = acos(dot(light.direction, light_to_fragment_direction)); -``` - -the first step of this is taking the dot product of light direction and the direction from the light to the fragment - -since both direction vectors are normalized, the dot product will be between -1.0 and 1.0 - -the dot product of two unit vectors is the cosine of the angle between them ([proof here](https://math.libretexts.org/Bookshelves/Calculus/Calculus_(OpenStax)/12%3A_Vectors_in_Space/12.03%3A_The_Dot_Product#Evaluating_a_Dot_Product)) - -therefore, we take the arccosine of that dot product to get the angle between the light and the fragment - -once we have this angle we can plug it in to a falloff based on the angle properties of the light: - -```wgsl -let angle_inner_factor = light.inner_angle/light.outer_angle; -let angle_factor = linear_falloff_radius(light_to_fragment_angle / light.outer_angle, angle_inner_factor))); -``` -```wgsl -fn linear_falloff_radius(factor: f32, radius: f32) -> f32 { - if factor < radius { - return 1.0; - } else { - return 1.0 - (factor - radius) / (1.0 - radius); - } -} -``` -next, we need to make sure the effect falls off properly over distance - -we can do this by getting the distance from the light to the fragment and normalizing it with the range of the light before plugging that into an inverse square falloff - -we'll use squared distance to avoid expensive and unnecessary square root operations: - -```wgsl -let light_distance_squared = distance_squared(in.world_position.xyz, light.position); -let distance_factor = inverse_falloff_radius(saturate(light_distance_squared / (light.range * light.range)), 0.5); -``` -```wgsl -fn distance_squared(a: vec3f, b: vec3f) -> f32 { - let vec = a - b; - return dot(vec, vec); -} - -fn inverse_falloff(factor: f32) -> f32 { - return pow(1.0 - factor, 2.0); -} - -fn inverse_falloff_radius(factor: f32, radius: f32) -> f32 { - if factor < radius { - return 1.0; - } else { - return inverse_falloff((factor - radius) / (1.0 - radius)); - } -} -``` - -now we'll have a float multiplier between 0.0 and 1.0 for our angle and distance to the light - -we can get the resulting color by multiplying these with the base color texture: - -```wgsl -let base_color = textureSample(base_texture, base_sampler, in.uv); -let final_color = base_color * angle_factor * distance_factor; -``` - -this works for one light, but we need to refactor it to loop over all the provided blacklights: -```wgsl -@fragment -fn fragment( - in: VertexOutput, -) -> @location(0) vec4<f32> { - let base_color = textureSample(base_texture, base_sampler, in.uv); - var final_color = vec4f(0.0, 0.0, 0.0, 0.0); - for (var i = u32(0); i < arrayLength(&lights); i = i+1) { - let light = lights[i]; - - let light_to_fragment_direction = normalize(in.world_position.xyz - light.position); - let light_to_fragment_angle = acos(dot(light.direction, light_to_fragment_direction)); - let angle_inner_factor = light.inner_angle / light.outer_angle; - let angle_factor = linear_falloff_radius(light_to_fragment_angle / light.outer_angle, angle_inner_factor); - - let light_distance_squared = distance_squared(in.world_position.xyz, light.position); - let distance_factor = inverse_falloff_radius(saturate(light_distance_squared / (light.range * light.range)), 0.5); - - final_color = saturate(final_color + base_color * angle_factor * distance_factor); - } - return final_color; -} -``` - -and with that, the shader is pretty much complete - -you can view the full completed shader code [here](https://github.com/soaosdev/bevy_blacklight_material/blob/master/assets/shaders/blacklight_material.wgsl) - -have fun! - diff --git a/content/projects/nix_aurea/index.md b/content/projects/nix_aurea/index.md deleted file mode 100644 index 2c68a6d..0000000 --- a/content/projects/nix_aurea/index.md +++ /dev/null @@ -1,11 +0,0 @@ -+++ -title = "nix_aurea" -[taxonomies] -categories = ["game"] -languages = ["rust"] -[extra] -wip = true -very_cool = true -+++ - -this page is under construction ;) |
