TextureState.cpp revision 138c21fbec12bead3c7ca1f181c3fd35542ccb00 
1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16#include "renderstate/TextureState.h"
17
18#include "Caches.h"
19#include "utils/TraceUtils.h"
20
21#include <GLES3/gl3.h>
22#include <memory>
23#include <SkCanvas.h>
24#include <SkBitmap.h>
25
26namespace android {
27namespace uirenderer {
28
29// Width of mShadowLutTexture, defines how accurate the shadow alpha lookup table is
30static const int SHADOW_LUT_SIZE = 128;
31
32// Must define as many texture units as specified by kTextureUnitsCount
33const GLenum kTextureUnits[] = {
34    GL_TEXTURE0,
35    GL_TEXTURE1,
36    GL_TEXTURE2,
37    GL_TEXTURE3
38};
39
40TextureState::TextureState()
41        : mTextureUnit(0) {
42    glActiveTexture(kTextureUnits[0]);
43    resetBoundTextures();
44
45    GLint maxTextureUnits;
46    glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &maxTextureUnits);
47    LOG_ALWAYS_FATAL_IF(maxTextureUnits < kTextureUnitsCount,
48            "At least %d texture units are required!", kTextureUnitsCount);
49    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
50}
51
52TextureState::~TextureState() {
53    if (mShadowLutTexture != nullptr) {
54        mShadowLutTexture->deleteTexture();
55    }
56}
57
58/**
59 * Maps shadow geometry 'alpha' varying (1 for darkest, 0 for transparent) to
60 * darkness at that spot. Input values of 0->1 should be mapped within the same
61 * range, but can affect the curve for a different visual falloff.
62 *
63 * This is used to populate the shadow LUT texture for quick lookup in the
64 * shadow shader.
65 */
66static float computeShadowOpacity(float ratio) {
67    // exponential falloff function provided by UX
68    float val = 1 - ratio;
69    return exp(-val * val * 4.0) - 0.018;
70}
71
72void TextureState::constructTexture(Caches& caches) {
73    if (mShadowLutTexture == nullptr) {
74        mShadowLutTexture.reset(new Texture(caches));
75
76        unsigned char bytes[SHADOW_LUT_SIZE];
77        for (int i = 0; i < SHADOW_LUT_SIZE; i++) {
78            float inputRatio = i / (SHADOW_LUT_SIZE - 1.0f);
79            bytes[i] = computeShadowOpacity(inputRatio) * 255;
80        }
81        mShadowLutTexture->upload(GL_ALPHA, SHADOW_LUT_SIZE, 1, GL_ALPHA, GL_UNSIGNED_BYTE, &bytes);
82        mShadowLutTexture->setFilter(GL_LINEAR);
83        mShadowLutTexture->setWrap(GL_CLAMP_TO_EDGE);
84    }
85}
86
87void TextureState::activateTexture(GLuint textureUnit) {
88    LOG_ALWAYS_FATAL_IF(textureUnit >= kTextureUnitsCount,
89            "Tried to use texture unit index %d, only %d exist",
90            textureUnit, kTextureUnitsCount);
91    if (mTextureUnit != textureUnit) {
92        glActiveTexture(kTextureUnits[textureUnit]);
93        mTextureUnit = textureUnit;
94    }
95}
96
97void TextureState::resetActiveTexture() {
98    mTextureUnit = -1;
99}
100
101void TextureState::bindTexture(GLuint texture) {
102    if (mBoundTextures[mTextureUnit] != texture) {
103        glBindTexture(GL_TEXTURE_2D, texture);
104        mBoundTextures[mTextureUnit] = texture;
105    }
106}
107
108void TextureState::bindTexture(GLenum target, GLuint texture) {
109    if (target == GL_TEXTURE_2D) {
110        bindTexture(texture);
111    } else {
112        // GLConsumer directly calls glBindTexture() with
113        // target=GL_TEXTURE_EXTERNAL_OES, don't cache this target
114        // since the cached state could be stale
115        glBindTexture(target, texture);
116    }
117}
118
119void TextureState::deleteTexture(GLuint texture) {
120    // When glDeleteTextures() is called on a currently bound texture,
121    // OpenGL ES specifies that the texture is then considered unbound
122    // Consider the following series of calls:
123    //
124    // glGenTextures -> creates texture name 2
125    // glBindTexture(2)
126    // glDeleteTextures(2) -> 2 is now unbound
127    // glGenTextures -> can return 2 again
128    //
129    // If we don't call glBindTexture(2) after the second glGenTextures
130    // call, any texture operation will be performed on the default
131    // texture (name=0)
132
133    unbindTexture(texture);
134
135    glDeleteTextures(1, &texture);
136}
137
138void TextureState::resetBoundTextures() {
139    for (int i = 0; i < kTextureUnitsCount; i++) {
140        mBoundTextures[i] = 0;
141    }
142}
143
144void TextureState::unbindTexture(GLuint texture) {
145    for (int i = 0; i < kTextureUnitsCount; i++) {
146        if (mBoundTextures[i] == texture) {
147            mBoundTextures[i] = 0;
148        }
149    }
150}
151
152} /* namespace uirenderer */
153} /* namespace android */
154
155