To create a shader for an item, you will need to create
- a
.glslfile to store shader code and - a
.jsonfile to denote which items to apply the shader to
These files should be placed under the items folder.
GLSL Format
The shader code will be injected into /shaders/lib/materials/materialHandling/entityMaterials.glsl.
The shader code is evaluated at every vertex of the item. In layman’s terms, the code is evaluated at every point on the item.
Inputs
You have access to the following within the shader code. The data type is indicated in front. This is a non-exhaustive list and only touches on the most commonly used variables.
int currentRenderedItemId - The item id of the item being rendered at, as assigned by Iris.
float frameTimeCounter - Tracks time passing within the game.
vec3 color.rgb - The color of the item within the item texture, for the currently evaluated part of the item. Each RGB value ranges between 0 and 1.
vec2 lmCoordM - The lightmap at the currently evaluated part of the item. x is the blocklight, y is the skylight.
vec3 playerPos + cameraPosition - The sum provides the world-space coordinates of the part of the item currently being evaluated.
vec2 signMidCoordPos - Provides the displacement from the centre of the texture being used on that surface of the item.
float NdotU - The value of the dot product between the vector normal to the item surface and the vector pointing upwards.
vec3 normalM - The vector normal to the item surface.
vec3 eastVec - The vector pointing eastwards.
float skyLightCheck - Ranges between 0 and 1 and checks for the presence of sky light.
sampler2D noisetex - Used as a source of randomness. Can be read using texture2D(noisetex, coord) where coord is a vec2. The g component varies slowly while r and b components vary quickly.
sampler2D tex - Used to read the entire texture file of the item, together with texelFetch. The size of tex can be obtained by textureSize(tex, 0).
vec2 texCoord - Gives the coordinate of the part of the item being read on the texture. Ranges between 0 and 1.
Outputs
The following can be modified within the code. The data type is indicated in front. This is a non-exhaustive list and only touches on the most commonly used variables.
float materialMask = OSIEBCA * x - x is an integer denoting the deferred material being applied on this item.
float emission - Handles emissivity of the item.
float smoothnessG - Handles strength of reflection by the sun and moon.
float smoothnessD - Handles strength of screenspace reflections.
float highlightMult - Controls strength of the multiplier for highlights.
vec2 lmCoordM - Used to modify the lightmap values.
vec3 color.rgb - Can be used to modify the color of the item.
int subsurfaceMode - Controls the type of subsurface scattering used. 1 is for leaves and general foliage, 2 is for lily pads and 3 is for vines as well as snow & ice (if the option is enabled).
boolean noSmoothLighting - Controls whether or not smooth lighting is applied.
boolean noDirectionalShading - Controls whether or not directional shading is applied.
float noiseFactor - Adjusts the amount of noise added when COATED_TEXTURES is enabled.
float purkinjeOverwrite - Overwrites the darkness desaturation effect if set to 1.0 for that part of the item.
JSON Format
The following are the parameters specified in the JSON. Bolded and italicized parameters are required.
name - The name of the type of item handled by the shader.
glsl - The relative path to the .glsl file. Currently only searches for files within the same folder as the .json file. or within a sub-folder of that folder.
mat<n> - Complementary Shaders divides the space of item IDs into blocks of block_size item IDs where block_size is a power of 2 and is at least 4. Each of these IDs are assigned to a list of entities and within the .glsl code, this can be checked with currentRenderedItemId % ... == ?.
blockSize - The number of item IDs this shader material will take up. Must be a power of 2 and greater than or equal to 4. If not specified, defaults to 4.