PolyList

Introduction

Stores the geometry data of a 3D mesh.

import PolyList from 'bg2e-js/ts/base/PolyList.ts';

const plist = new PolyList();

list.vertex = [
    1, 0, 0,
    0, 1, 0,
    1, 1, 0
];

plist.normal = [
    0, 0, 1,
    0, 0, 1,
    0, 0, 1
];

plist.texCoord0 = [
    1, 0,
    0, 1,
    1, 1
];

plist.index = [
    0, 1, 2
];

console.log(plist.vertex);
console.log(plist.normal);
console.log(plist.texCoord0);

The tangent array is generated automatically using the vertex and texCoord0 arrrays. For that reason, if the mesh does not have texture coordinate information, it will not be possible to generate tangents, and this may cause display problems when using shaders that require tangents (e.g. displacement maps, normal maps or bump maps).

Reference

Exported objects

import { BufferType, DrawMode } from 'bg2e-js/ts/base/PolyList.ts';

BufferType: Identifies a buffer type. It is not used directly in the PolyList class, but it is used in other elements of the graphics engine, for example, when marking input attributes in a shader.

• BufferType.VERTEX Vertex buffer
• BufferType.NORMAL Normal buffer
• BufferType.TEX_COORD_0 Texture coordinates 0 buffer
• BufferType.TEX_COORD_1 Texture coordinates 1 buffer
• BufferType.TEX_COORD_2 Texture coordinates 2 buffer
• BufferType.COLOR Color buffer
• BufferType.TANGENT Tangent buffer
• BufferType.INDEX Index buffer

DrawMode: Used to specify the settings to be used by the graphics engine to draw the geometry contained in the polyList.

• DrawMode.TRIANGLES
• DrawMode.TRIANGLE_FAN
• DrawMode.TRIANGLE_STRIP
• DrawMode.LINES
• DrawMode.LINE_STRIP

PolyList attributes

Metadata attributes

Metadata attributes are used for mesh cataloging and to provide miscellaneous information to the graphics engine or application. They do not influence the display of the object.

plist.name: (read/write)

plist.groupName: (read/write)

Geometric attributes

Geometric attributes are used to determine the shape of the mesh, and attributes that depend on geometric information, for example, the position in space of vertices in local coordinates, texture coordinates or the drawing mode (DrawMode).

plist.drawMode: (read/write)

plist.vertex: (read/write)

plist.normal: (read/write)

plist.texCoord0: (read/write)

plist.texCoord1: (read/write)

plist.texCoord2: (read/write)

plist.color: (read/write)

plist.index: (read/write)

plist.tangent: (read) Gets the tangent array, which is generated from the vertex array, texCoord0 and indexes. It is recommended that you do not use this accessor until you have configured the rest of the arrays. If changes are made to these arrays, and the new array length is the same as the old one, the tangents array must be regenerated (see rebuildTangents() function).

plist.validTangents: (read) Returns true if the tangent array is valid, or false otherwise. The tangent array is invalid when it does not exist, or its size does not match the vertex or texture coordinate arrays. If the tangents are invalid, it will be automatically regenerated the next time the tangents are obtained using the tangent attribute.

Material attributes

Some display attributes that do not depend on the mesh may be processed in the mesh for efficiency reasons. For example, if a mesh is hidden, it is better not to send any information to the renderer than to ignore the output in the fragment shader. These attributes are stored in the mesh.

plist.visible: (read/write)

plist.visibleToShadows: (read/write)

Functions

plist.clone(): Creates and returns a copy of plist.

plist.assign(other): Assigns the other mesh attributes to plist, and rebuild the tangent vectors.

plist.rebuildTangents(): Re-generates the tangents. When the array of vertices and/or texture coordinates is modified, it may happen that the tangents are still valid. To check if the tangents are valid, only three conditions are taken into account: that the tangent array is not null, that its size matches the vertex array and that its size matches the texture coordinate array.

However, it may be the case that texture coordinates or vertices are changed, but the size of the array is not changed (for example, if the number of vertices is the same, but the positions change). In this case, the tangent array will remain valid and unchanged, but the tangent information will not be consistent with the new geometry. In these cases, the rebuildTangents() function must be called manually.

Static functions

PolyList.ApplyTransform(plist, trx): Modify the vertex, normal and tangent arrays of the plist mesh with the transformation matrix trx.

Render layers

Render layers are used internally by the graphics engine to decide when a PolyList has to be rendered or not. It is an internal tool that is not handled by the serialization and deserialization functions.

For example, internally the graphics engine will use these layers to configure if a polyList has to be rendered in a certain render pass, depending on other properties, and on the specific render pass. If a polyList has material properties that make it transparent, then internally the render layer will be configured to only be drawn when objects are rendered in the transparency render pass.

The render layers are a 32-bit mask, so there are 32 possible render layers.

The renderLayers default value is RenderLayer.ALL, so by default, a poly list are always rendererd.

polyList.renderLayers (read/write): Sets the active rendering layers for the polyList:

import { RenderLayer } from 'bg2e/base/PolyList';
...
myPolyList.renderLayers = RenderLayer.LAYER_0 | RenderLayer.LAYER_1;

polyList.enableLayer(layer): activa una o varias capas de render mediante una operación OR sobre el valor actual de renderLayer.

// myPolyList.renderLayers == 0b00000000000000000000000000000000
myPolyList.enableLayer(RenderLayer.LAYER_0 | RenderLayer.LAYER_1);
// myPolyList.renderLayers == 0b00000000000000000000000000000011

polyList.disableLayer(layer): disables one or more render layers by means of a 1’s complement AND operation on the current value of renderLayer.

// myPolyList.renderLayers == 0b11111111111111111111111111111111
myPolyList.disableLayer(RenderLayer.LAYER_0 | RenderLayer.LAYER_1);
// myPolyList.renderLayers == 0b11111111111111111111111111111100