/*
* Copyright 2003-2006, 2009, 2017, United States Government, as represented by the Administrator of the
* National Aeronautics and Space Administration. All rights reserved.
*
* The NASAWorldWind/WebWorldWind platform is licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @exports StarFieldProgram
*/
define([
'../error/ArgumentError',
'../shaders/GpuProgram',
'../util/Logger'
],
function (ArgumentError,
GpuProgram,
Logger) {
"use strict";
/**
* Constructs a new program.
* Initializes, compiles and links this GLSL program with the source code for its vertex and fragment shaders.
* <p>
* This method creates WebGL shaders for the program's shader sources and attaches them to a new GLSL program.
* This method then compiles the shaders and then links the program if compilation is successful.
* Use the bind method to make the program current during rendering.
*
* @alias StarFieldProgram
* @constructor
* @augments GpuProgram
* @classdesc StarFieldProgram is a GLSL program that draws points representing stars.
* @param {WebGLRenderingContext} gl The current WebGL context.
* @throws {ArgumentError} If the shaders cannot be compiled, or linking of the compiled shaders into a program
* fails.
*/
var StarFieldProgram = function (gl) {
var vertexShaderSource =
//.x = declination
//.y = right ascension
//.z = point size
//.w = magnitude
'attribute vec4 vertexPoint;\n' +
'uniform mat4 mvpMatrix;\n' +
//number of days (positive or negative) since Greenwich noon, Terrestrial Time,
// on 1 January 2000 (J2000.0)
'uniform float numDays;\n' +
'uniform vec2 magnitudeRange;\n' +
'varying float magnitudeWeight;\n' +
//normalizes an angle between 0.0 and 359.0
'float normalizeAngle(float angle) {\n' +
' float angleDivisions = angle / 360.0;\n' +
' return 360.0 * (angleDivisions - floor(angleDivisions));\n' +
'}\n' +
//transforms declination and right ascension in cartesian coordinates
'vec3 computePosition(float dec, float ra) {\n' +
' float GMST = normalizeAngle(280.46061837 + 360.98564736629 * numDays);\n' +
' float GHA = normalizeAngle(GMST - ra);\n' +
' float lon = -GHA + 360.0 * step(180.0, GHA);\n' +
' float latRad = radians(dec);\n' +
' float lonRad = radians(lon);\n' +
' float radCosLat = cos(latRad);\n' +
' return vec3(radCosLat * sin(lonRad), sin(latRad), radCosLat * cos(lonRad));\n' +
'}\n' +
//normalizes a value between 0.0 and 1.0
'float normalizeScalar(float value, float minValue, float maxValue){\n' +
' return (value - minValue) / (maxValue - minValue);\n' +
'}\n' +
'void main() {\n' +
' vec3 vertexPosition = computePosition(vertexPoint.x, vertexPoint.y);\n' +
' gl_Position = mvpMatrix * vec4(vertexPosition.xyz, 1.0);\n' +
' gl_Position.z = gl_Position.w - 0.00001;\n' +
' gl_PointSize = vertexPoint.z;\n' +
' magnitudeWeight = normalizeScalar(vertexPoint.w, magnitudeRange.x, magnitudeRange.y);\n' +
'}',
fragmentShaderSource =
'precision mediump float;\n' +
'uniform sampler2D textureSampler;\n' +
'uniform int textureEnabled;\n' +
'varying float magnitudeWeight;\n' +
'const vec4 white = vec4(1.0, 1.0, 1.0, 1.0);\n' +
'const vec4 grey = vec4(0.5, 0.5, 0.5, 1.0);\n' +
'void main() {\n' +
' if (textureEnabled == 1) {\n' +
' gl_FragColor = texture2D(textureSampler, gl_PointCoord);\n' +
' }\n' +
' else {\n' +
//paint the starts in shades of grey, where the brightest star is white and the dimmest star is grey
' gl_FragColor = mix(white, grey, magnitudeWeight);\n' +
' }\n' +
'}';
// Call to the superclass, which performs shader program compiling and linking.
GpuProgram.call(this, gl, vertexShaderSource, fragmentShaderSource, ["vertexPoint"]);
/**
* The WebGL location for this program's 'vertexPoint' attribute.
* @type {Number}
* @readonly
*/
this.vertexPointLocation = this.attributeLocation(gl, "vertexPoint");
/**
* The WebGL location for this program's 'mvpMatrix' uniform.
* @type {WebGLUniformLocation}
* @readonly
*/
this.mvpMatrixLocation = this.uniformLocation(gl, "mvpMatrix");
/**
* The WebGL location for this program's 'numDays' uniform.
* @type {WebGLUniformLocation}
* @readonly
*/
this.numDaysLocation = this.uniformLocation(gl, "numDays");
/**
* The WebGL location for this program's 'magnitudeRangeLocation' uniform.
* @type {WebGLUniformLocation}
* @readonly
*/
this.magnitudeRangeLocation = this.uniformLocation(gl, "magnitudeRange");
/**
* The WebGL location for this program's 'textureSampler' uniform.
* @type {WebGLUniformLocation}
* @readonly
*/
this.textureUnitLocation = this.uniformLocation(gl, "textureSampler");
/**
* The WebGL location for this program's 'textureEnabled' uniform.
* @type {WebGLUniformLocation}
* @readonly
*/
this.textureEnabledLocation = this.uniformLocation(gl, "textureEnabled");
};
/**
* A string that uniquely identifies this program.
* @type {string}
* @readonly
*/
StarFieldProgram.key = "WorldWindGpuStarFieldProgram";
// Inherit from GpuProgram.
StarFieldProgram.prototype = Object.create(GpuProgram.prototype);
/**
* Loads the specified matrix as the value of this program's 'mvpMatrix' uniform variable.
*
* @param {WebGLRenderingContext} gl The current WebGL context.
* @param {Matrix} matrix The matrix to load.
* @throws {ArgumentError} If the specified matrix is null or undefined.
*/
StarFieldProgram.prototype.loadModelviewProjection = function (gl, matrix) {
if (!matrix) {
throw new ArgumentError(
Logger.logMessage(Logger.LEVEL_SEVERE, "StarFieldProgram", "loadModelviewProjection", "missingMatrix"));
}
this.loadUniformMatrix(gl, matrix, this.mvpMatrixLocation);
};
/**
* Loads the specified number as the value of this program's 'numDays' uniform variable.
*
* @param {WebGLRenderingContext} gl The current WebGL context.
* @param {Number} numDays The number of days (positive or negative) since Greenwich noon, Terrestrial Time,
* on 1 January 2000 (J2000.0)
* @throws {ArgumentError} If the specified number is null or undefined.
*/
StarFieldProgram.prototype.loadNumDays = function (gl, numDays) {
if (numDays == null) {
throw new ArgumentError(
Logger.logMessage(Logger.LEVEL_SEVERE, "StarFieldProgram", "loadNumDays", "missingNumDays"));
}
gl.uniform1f(this.numDaysLocation, numDays);
};
/**
* Loads the specified numbers as the value of this program's 'magnitudeRange' uniform variable.
*
* @param {WebGLRenderingContext} gl The current WebGL context.
* @param {Number} minMag
* @param {Number} maxMag
* @throws {ArgumentError} If the specified numbers are null or undefined.
*/
StarFieldProgram.prototype.loadMagnitudeRange = function (gl, minMag, maxMag) {
if (minMag == null) {
throw new ArgumentError(
Logger.logMessage(Logger.LEVEL_SEVERE, "StarFieldProgram", "loadMagRange", "missingMinMag"));
}
if (maxMag == null) {
throw new ArgumentError(
Logger.logMessage(Logger.LEVEL_SEVERE, "StarFieldProgram", "loadMagRange", "missingMaxMag"));
}
gl.uniform2f(this.magnitudeRangeLocation, minMag, maxMag);
};
/**
* Loads the specified number as the value of this program's 'textureSampler' uniform variable.
* @param {WebGLRenderingContext} gl The current WebGL context.
* @param {Number} unit The texture unit.
*/
StarFieldProgram.prototype.loadTextureUnit = function (gl, unit) {
gl.uniform1i(this.textureUnitLocation, unit - gl.TEXTURE0);
};
/**
* Loads the specified boolean as the value of this program's 'textureEnabledLocation' uniform variable.
* @param {WebGLRenderingContext} gl The current WebGL context.
* @param {Boolean} value
*/
StarFieldProgram.prototype.loadTextureEnabled = function (gl, value) {
gl.uniform1i(this.textureEnabledLocation, value ? 1 : 0);
};
return StarFieldProgram;
});