thi-ng/umbrella

import {
    diffuseLighting,
    halfLambert,
    lambert,
} from "@thi.ng/shader-ast-stdlib/light/lambert";
import { transformMVP } from "@thi.ng/shader-ast-stdlib/matrix/mvp";
import { surfaceNormal } from "@thi.ng/shader-ast-stdlib/matrix/normal";
import { M4, S2D, V2, V3 } from "@thi.ng/shader-ast/api/types";
import { assign } from "@thi.ng/shader-ast/ast/assign";
import { defMain } from "@thi.ng/shader-ast/ast/function";
import { vec4 } from "@thi.ng/shader-ast/ast/lit";
import { mul } from "@thi.ng/shader-ast/ast/ops";
import { $ } from "@thi.ng/shader-ast/ast/swizzle";
import { normalize } from "@thi.ng/shader-ast/builtin/math";
import { texture } from "@thi.ng/shader-ast/builtin/texture";
import type { Material } from "../api/material.js";
import type { ShaderPresetOpts, ShaderSpec } from "../api/shader.js";
import { defMaterial } from "../material.js";
import { autoNormalMatrix2 } from "../matrices.js";
import { colorAttrib, positionAttrib } from "../utils.js";

export interface LambertOpts
    extends ShaderPresetOpts<Pick<Material, "ambientCol" | "diffuseCol">> {
    bidir: boolean;
}

export const LAMBERT = (opts: Partial<LambertOpts> = {}): ShaderSpec => ({
    vs: (gl, unis, ins, outs) => [
        defMain(() => [
            opts.uv ? assign(outs.vuv, ins[opts.uv]) : null,
            assign(outs.vcolor, colorAttrib(opts, ins, unis.diffuseCol)),
            assign(outs.vnormal, surfaceNormal(ins.normal, unis.normalMat)),
            assign(
                gl.gl_Position,
                transformMVP(
                    positionAttrib(opts, ins),
                    unis.model,
                    unis.view,
                    unis.proj
                )
            ),
        ]),
    ],
    fs: (_, unis, ins, outs) => [
        defMain(() => [
            assign(
                outs.fragColor,
                vec4(
                    diffuseLighting(
                        (opts.bidir !== false ? halfLambert : lambert)(
                            normalize(ins.vnormal),
                            unis.lightDir
                        ),
                        opts.uv
                            ? mul(
                                    $(texture(unis.tex, ins.vuv), "xyz"),
                                    ins.vcolor
                              )
                            : ins.vcolor,
                        unis.lightCol,
                        unis.ambientCol
                    ),
                    1
                )
            ),
        ]),
    ],
    // pre: ALIAS_TEXTURE,
    attribs: {
        position: V3,
        normal: V3,
        ...(opts.uv ? { [opts.uv]: V2 } : null),
        ...(opts.color && !opts.instanceColor ? { [opts.color]: V3 } : null),
        ...(opts.instancePos ? { [opts.instancePos]: V3 } : null),
        ...(opts.instanceColor ? { [opts.instanceColor]: V3 } : null),
    },
    varying: {
        vcolor: V3,
        vnormal: V3,
        ...(opts.uv ? { vuv: V2 } : null),
    },
    uniforms: {
        model: M4,
        view: M4,
        proj: M4,
        normalMat: [M4, autoNormalMatrix2()],
        lightDir: [V3, [0, 1, 0]],
        lightCol: [V3, [1, 1, 1]],
        ...defMaterial(
            { diffuseCol: [1, 1, 1], ...opts.material },
            { specularCol: false }
        ),
        ...(opts.uv ? { tex: S2D } : null),
    },
    state: {
        depth: true,
        cull: true,
        ...opts.state,
    },
});