three.js/src/renderers/webgl/WebGLCapabilities.js

/**
 * @author mrdoob / http://mrdoob.com/
 */

function WebGLCapabilities( gl, extensions, parameters ) {

	var maxAnisotropy;

	function getMaxAnisotropy() {

		if ( maxAnisotropy !== undefined ) return maxAnisotropy;

		var extension = extensions.get( 'EXT_texture_filter_anisotropic' );

		if ( extension !== null ) {

			maxAnisotropy = gl.getParameter( extension.MAX_TEXTURE_MAX_ANISOTROPY_EXT );

		} else {

			maxAnisotropy = 0;

		}

		return maxAnisotropy;

	}

	function getMaxPrecision( precision ) {

		if ( precision === 'highp' ) {

			if ( gl.getShaderPrecisionFormat( gl.VERTEX_SHADER, gl.HIGH_FLOAT ).precision > 0 &&
				gl.getShaderPrecisionFormat( gl.FRAGMENT_SHADER, gl.HIGH_FLOAT ).precision > 0 ) {

				return 'highp';

			}

			precision = 'mediump';

		}

		if ( precision === 'mediump' ) {

			if ( gl.getShaderPrecisionFormat( gl.VERTEX_SHADER, gl.MEDIUM_FLOAT ).precision > 0 &&
				gl.getShaderPrecisionFormat( gl.FRAGMENT_SHADER, gl.MEDIUM_FLOAT ).precision > 0 ) {

				return 'mediump';

			}

		}

		return 'lowp';

	}

	/* eslint-disable no-undef */
	var isWebGL2 = ( typeof WebGL2RenderingContext !== 'undefined' && gl instanceof WebGL2RenderingContext ) ||
		( typeof WebGL2ComputeRenderingContext !== 'undefined' && gl instanceof WebGL2ComputeRenderingContext );
	/* eslint-enable no-undef */

	var precision = parameters.precision !== undefined ? parameters.precision : 'highp';
	var maxPrecision = getMaxPrecision( precision );

	if ( maxPrecision !== precision ) {

		console.warn( 'THREE.WebGLRenderer:', precision, 'not supported, using', maxPrecision, 'instead.' );
		precision = maxPrecision;

	}

	var logarithmicDepthBuffer = parameters.logarithmicDepthBuffer === true;

	var maxTextures = gl.getParameter( gl.MAX_TEXTURE_IMAGE_UNITS );
	var maxVertexTextures = gl.getParameter( gl.MAX_VERTEX_TEXTURE_IMAGE_UNITS );
	var maxTextureSize = gl.getParameter( gl.MAX_TEXTURE_SIZE );
	var maxCubemapSize = gl.getParameter( gl.MAX_CUBE_MAP_TEXTURE_SIZE );

	var maxAttributes = gl.getParameter( gl.MAX_VERTEX_ATTRIBS );
	var maxVertexUniforms = gl.getParameter( gl.MAX_VERTEX_UNIFORM_VECTORS );
	var maxVaryings = gl.getParameter( gl.MAX_VARYING_VECTORS );
	var maxFragmentUniforms = gl.getParameter( gl.MAX_FRAGMENT_UNIFORM_VECTORS );

	var vertexTextures = maxVertexTextures > 0;
	var floatFragmentTextures = isWebGL2 || !! extensions.get( 'OES_texture_float' );
	var floatVertexTextures = vertexTextures && floatFragmentTextures;

	var maxSamples = isWebGL2 ? gl.getParameter( gl.MAX_SAMPLES ) : 0;

	return {

		isWebGL2: isWebGL2,

		getMaxAnisotropy: getMaxAnisotropy,
		getMaxPrecision: getMaxPrecision,

		precision: precision,
		logarithmicDepthBuffer: logarithmicDepthBuffer,

		maxTextures: maxTextures,
		maxVertexTextures: maxVertexTextures,
		maxTextureSize: maxTextureSize,
		maxCubemapSize: maxCubemapSize,

		maxAttributes: maxAttributes,
		maxVertexUniforms: maxVertexUniforms,
		maxVaryings: maxVaryings,
		maxFragmentUniforms: maxFragmentUniforms,

		vertexTextures: vertexTextures,
		floatFragmentTextures: floatFragmentTextures,
		floatVertexTextures: floatVertexTextures,

		maxSamples: maxSamples

	};

}


export { WebGLCapabilities };