package decal

import org.openrndr.application
import org.openrndr.draw.DrawPrimitive
import org.openrndr.draw.isolated
import org.openrndr.draw.shadeStyle
import org.openrndr.extra.camera.Orbital
import org.openrndr.extra.objloader.loadOBJMeshData
import org.openrndr.extra.mesh.toVertexBuffer
import org.openrndr.extra.meshgenerators.decal.decal
import org.openrndr.math.Vector3
import org.openrndr.math.transforms.buildTransform
import java.io.File
import kotlin.math.PI

/**
 * Demonstrate decal generation and rendering
 * @see <img src="https://raw.githubusercontent.com/openrndr/orx/media/orx-mesh-generators/images/decal-DemoDecal02Kt.png">
 */
fun main() = application {
    configure {
        width = 720
        height = 720
    }
    program {
        /** base object */
        val obj = loadOBJMeshData(File("demo-data/obj-models/suzanne/Suzanne.obj"))
            .toMeshData() // convert from CompoundMeshData to MeshData
            .triangulate() // convert to triangles, we need this for the decal generation steps

        /** object [VertexBuffer] */
        val objVB = obj.toVertexBuffer()


        /** positions for the decal projectors */
        val decalPositions = listOf(
            Vector3(0.35, 0.245, 0.8),
            Vector3(-0.35, 0.245, 0.8)
        )

        /** decal vertex buffers */
        val decalVBs = decalPositions.map {
            val projector = buildTransform {
                translate(it)
            }
            val decal = obj.decal(projector, Vector3(2.0, 2.0, 0.5))
            val vb = decal.toVertexBuffer()
            vb
        }

        extend(Orbital()) {
            eye = Vector3(0.0, 0.0, 2.0)
        }
        extend {
            /* draw the base mesh */
            drawer.isolated {
                drawer.shadeStyle = shadeStyle {
                    fragmentTransform = """x_fill.rgb = vec3(v_viewNormal * 0.5 + 0.5); """
                }
                drawer.vertexBuffer(objVB, DrawPrimitive.TRIANGLES)
            }

            /* draw the decals */
            drawer.isolated {
                for ((index, decal) in decalVBs.withIndex()) {
                    /* offset the projection transform to avoid z-fighting */
                    drawer.projection = buildTransform {
                        translate(0.0, 0.0, -1e-4)
                    } * drawer.projection

                    /* draw effects on the decal geometry */
                    drawer.shadeStyle = shadeStyle {
                        fragmentTransform = """
                                float d = length(va_texCoord0.xy - vec2(0.5));
                                float sd = smoothstep(-0.01, 0.01, cos(p_time + d * 3.1415 * 2.0 * 10.0));
                                float l = max(0.0, va_normal.z);
                                x_fill = vec4(0.0, 0.0, 0.0, l * sd * 0.5); """
                        parameter("time", seconds * PI * 2 + index * PI)
                    }
                    drawer.vertexBuffer(decal, DrawPrimitive.TRIANGLES)
                }
            }
        }
    }
}