3D 效果的壁纸 本文实现的效果该原创文章首发于微信公众号:字节流动
偶然间,看到技术交流群里的一位同学在做类似于上图所示的 3D 效果壁纸,乍一看效果确实挺惊艳的。当时看到素材之后,马上就萌生了一个想法:利用 OpenGL 做一个能与之媲美的 3D 效果。
拿到素材之后,就开始撸代码,想着就是简单的图像绘制加上矩阵变换嘛,花半个小时搞定它,谁曾想故事远没那么简单。另外,这里特别感谢交流群里的 @1234 同学,提供了本文所需的素材。
3D 效果实现原理
毫无疑问,这种 3D 效果选择使用 OpenGL 实现是再合适不过了,当然 Vulkan 也挺香的。通过观察上图 3D 壁纸的效果,罗列一下我们可能要用到的技术点:
绘制原理图基于 3D 壁纸的效果画出以上原理图,每一次渲染包含 3 次小的绘制,即分别绘制背景层、人像层和外层。手机晃动时,通过 Java 层 API 获取重力传感器数据(不是加速度传感器),控制 3 张图像在平面四个方向的偏移,从背景层到外层偏移程度依次增大,从而给人一种 3D 的层次感。
Android 设备重力传感器数据的获取方法:
@Override
protected void onResume() {
super.onResume();
mSensorManager.registerListener(this,
mSensorManager.getDefaultSensor(Sensor.TYPE_GRAVITY),
SensorManager.SENSOR_DELAY_FASTEST);
}
@Override
protected void onPause() {
super.onPause();
mSensorManager.unregisterListener(this);
}
@Override
public void onSensorChanged(SensorEvent event) {
switch (event.sensor.getType()) {
case Sensor.TYPE_GRAVITY:
Log.d(TAG, "onSensorChanged() called with TYPE_GRAVITY: [x,y,z] = [" + event.values[0] + ", " + event.values[1] + ", " + event.values[2] + "]");
if(mSampleSelectedIndex + SAMPLE_TYPE == SAMPLE_TYPE_KEY_AVATAR)
{
mGLRender.setGravityXY(event.values[0], event.values[1]);
}
break;
}
}
另外,通过观察效果图还发现,3 张图像还有周期性的缩放,并且背景层、外层和人像层的缩放程度大小相反,这种做法也是为了强化 3D 效果。
使用 Native 层的变换矩阵,用于控制图像位移和缩放。
/**
*
* @param mvpMatrix
* @param angleX 绕X轴旋转度数
* @param angleY 绕Y轴旋转度数
* @param transX 沿X轴位移大小
* @param transY 沿Y轴位移大小
* @param ratio 宽高比
*/
void AvatarSample::UpdateMVPMatrix(glm::mat4 &mvpMatrix, int angleX, int angleY, float transX, float transY, float ratio)
{
LOGCATE("AvatarSample::UpdateMVPMatrix angleX = %d, angleY = %d, ratio = %f", angleX, angleY, ratio);
angleX = angleX % 360;
angleY = angleY % 360;
//转化为弧度角
float radiansX = static_cast<float>(MATH_PI / 180.0f * angleX);
float radiansY = static_cast<float>(MATH_PI / 180.0f * angleY);
// Projection matrix
glm::mat4 Projection = glm::ortho(-1.0f, 1.0f, -1.0f, 1.0f, 0.1f, 100.0f);
//glm::mat4 Projection = glm::frustum(-ratio, ratio, -1.0f, 1.0f, 4.0f, 100.0f);
//glm::mat4 Projection = glm::perspective(45.0f,ratio, 0.1f,100.f);
// View matrix
glm::mat4 View = glm::lookAt(
glm::vec3(0, 0, 4), // Camera is at (0,0,1), in World Space
glm::vec3(0, 0, 0), // and looks at the origin
glm::vec3(0, 1, 0) // Head is up (set to 0,-1,0 to look upside-down)
);
// Model matrix
glm::mat4 Model = glm::mat4(1.0f);
Model = glm::scale(Model, glm::vec3(m_ScaleX, m_ScaleY, 1.0f));//m_ScaleX, m_ScaleY 用于控制 x,y 方向上的缩放
Model = glm::rotate(Model, radiansX, glm::vec3(1.0f, 0.0f, 0.0f));
Model = glm::rotate(Model, radiansY, glm::vec3(0.0f, 1.0f, 0.0f));
Model = glm::translate(Model, glm::vec3(transX, transY, 0.0f));
mvpMatrix = Projection * View * Model;
}
素材图里的人像层和外层是部分区域透明的 PNG 图,而背景层是每个像素透明度均为最大值的 JPG 图。所以,在绘制 3 张图时,要先绘制背景层,然后依次是人像层、外层,为了防止遮挡,在绘制人像层、外层时需要利用片段着色器来丢弃透明度比较低的片元,这种操作俗称 alpha 测试。
用于 Alpha 测试的着色器脚本。
//顶点着色器
#version 300 es
layout(location = 0) in vec4 a_position;
layout(location = 1) in vec2 a_texCoord;
uniform mat4 u_MVPMatrix;
out vec2 v_texCoord;
void main()
{
gl_Position = u_MVPMatrix * a_position;
v_texCoord = a_texCoord;
}
//片段着色器
#version 300 es
precision highp float;
in vec2 v_texCoord;
layout(location = 0) out vec4 outColor;
uniform sampler2D s_TextureMap;
void main()
{
outColor = texture(s_TextureMap, v_texCoord);
if (outColor.a < 0.6) discard;//丢弃透明度比较低的片元
}
3D 效果实现
基于上节原理和知识点准备,我们使用下面的代码绘制 3D 效果。
void AvatarSample::Draw(int screenW, int screenH)
{
LOGCATE("AvatarSample::Draw()");
if(m_ProgramObj == GL_NONE) return;
float dScaleLevel = m_FrameIndex % 200 * 1.0f / 1000 + 0.0001f;
float scaleLevel = 1.0;
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_STENCIL_BUFFER_BIT | GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Use the program object
glUseProgram(m_ProgramObj);
glBindVertexArray(m_VaoId);
//1. 背景层的绘制
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[0]);
glUniform1i(m_SamplerLoc, 0);
//缩放控制
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.4f;
//设置变换矩阵 m_TransX m_TransY 为 x,y 方向的重力传感器数据
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX / 2, m_TransY / 2, (float)screenW / screenH);
glUniformMatrix4fv(m_MVPMatLoc, 1, GL_FALSE, &m_MVPMatrix[0][0]);
//绘制
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
//2. 人像层的绘制
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[1]);
glUniform1i(m_SamplerLoc, 1);
//缩放控制 pow(-1, m_FrameIndex / 200 + 1) 控制人像层的缩放大小跟背景层和外层相反
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200 + 1));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.4f;
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX * 1.2f, m_TransY * 1.2f, (float)screenW / screenH);
glUniformMatrix4fv(m_MVPMatLoc, 1, GL_FALSE, &m_MVPMatrix[0][0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
//3. 外层的绘制
glActiveTexture(GL_TEXTURE2);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[2]);
glUniform1i(m_SamplerLoc, 2);
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.8f;
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX * 2.5f, m_TransY * 2.5f, (float)screenW / screenH);
glUniformMatrix4fv(m_MVPMatLoc, 1, GL_FALSE, &m_MVPMatrix[0][0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
m_FrameIndex ++;
}
绘制效果如下图所示,我们期望的缩放和位移基本上实现了,但是仔细对比原效果图,很容易发现一些问题:最外层的白斑缺少一种模糊的过度,并且白点的亮度也不够。
初版效果图说到模糊效果,之前在介绍相机滤镜那篇文章里说过一种最简单的叠加偏移模糊,我们可以在绘制外层图像时,使用这种模糊效果。另外,参考效果图后,为了使白斑变的更大更亮,我们还需要用到混合和光照。
绘制外层图像的片段着色器如下,着色器中,我们通过放宽 alpha 值过滤范围,使白斑变的更大,同时将输出颜色叠加一定的强度值,使白斑变的更亮。
//绘制外层图像的片段着色器
#version 300 es
precision highp float;
layout(location = 0) out vec4 outColor;
in vec2 v_texCoord;
uniform sampler2D s_TextureMap;
void main() {
vec4 sample0, sample1, sample2, sample3;
float blurStep = 0.2;
float step = blurStep / 100.0;
sample0 = texture(s_TextureMap, vec2(v_texCoord.x - step, v_texCoord.y - step));
sample1 = texture(s_TextureMap, vec2(v_texCoord.x + step, v_texCoord.y + step));
sample2 = texture(s_TextureMap, vec2(v_texCoord.x + step, v_texCoord.y - step));
sample3 = texture(s_TextureMap, vec2(v_texCoord.x - step, v_texCoord.y + step));
outColor = (sample0 + sample1 + sample2 + sample3) / 4.0;
if (outColor.a > 0.03) //放宽 alpha 值过滤范围,使白斑变的更大
{
outColor += vec4(0.1, 0.1, 0.1, 0.0); //叠加一些强度,使白斑变的更亮
}
else
{
discard;
}
}
修改外层图像的绘制逻辑,添加混合。
//开启混合
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
//使用新的着色器程序
glUseProgram(m_BlurProgramObj);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[2]);
GLUtils::setFloat(m_BlurProgramObj, "s_TextureMap", 0);
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.8f;
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX * 2.5f, m_TransY * 2.5f, (float)screenW / screenH);
GLUtils::setMat4(m_BlurProgramObj, "u_MVPMatrix", m_MVPMatrix);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
//关闭混合
glDisable(GL_BLEND);
添加模糊和混合之后的绘制结果如下,看着效果符合预期,顿时有那么一点点成就感。
第二版效果图
正当我以为故事圆满结束的时候,旁边的小伙伴不屑地看了看我做的效果,并对比了下原效果图,然后一脸坏笑的说:“你看,人家做的背景还有形变啊!”,我心里顿时一句“卧槽”。
然后我仔细观察了下原效果图的背景形变,想起来之前在介绍 EGL 那篇文章里做过一种简单的正余弦形变,形变效果如下图所示。
旋转形变
做背景形变用到的片段着色器,需要传入图像分辨率、控制形变的标志位以及旋转角度,其中旋转角度需要与重力传感器数据绑定,实现晃动手机出现相关的动态背景形变。
//片段着色器
#version 300 es
precision highp float;
in vec2 v_texCoord;
layout(location = 0) out vec4 outColor;
uniform sampler2D s_TextureMap;
uniform vec2 u_texSize;//图像分辨率
uniform float u_needRotate;//判断是否需要做形变
uniform float u_rotateAngle;//通过旋转角度控制形变的程度
vec2 rotate(float radius, float angle, vec2 texSize, vec2 texCoord)
{
vec2 newTexCoord = texCoord;
vec2 center = vec2(texSize.x / 2.0, texSize.y / 2.0);
vec2 tc = texCoord * texSize;
tc -= center;
float dist = length(tc);
if (dist < radius) {
float percent = (radius - dist) / radius;
float theta = percent * percent * angle * 8.0;
float s = sin(theta);
float c = cos(theta);
tc = vec2(dot(tc, vec2(c, -s)), dot(tc, vec2(s, c)));
tc += center;
newTexCoord = tc / texSize;
}
return newTexCoord;
}
void main()
{
vec2 texCoord = v_texCoord;
if(u_needRotate > 0.0)
{
texCoord = rotate(0.5, u_rotateAngle, u_texSize, v_texCoord);
}
outColor = texture(s_TextureMap, texCoord);
if (outColor.a < 0.6) discard;
}
基于以上的着色器,我们单独绘制背景图,令形变的旋转角度与重力传感器数据绑定,效果如下图所示。
背景形变图综合了以上场景,我们最终的绘制逻辑如下:
void AvatarSample::Draw(int screenW, int screenH)
{
LOGCATE("AvatarSample::Draw()");
if(m_ProgramObj == GL_NONE) return;
float dScaleLevel = m_FrameIndex % 200 * 1.0f / 1000 + 0.0001f;
float scaleLevel = 1.0;
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_STENCIL_BUFFER_BIT | GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(m_ProgramObj);
glBindVertexArray(m_VaoId);
//1. 背景层的绘制
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[0]);
glUniform1i(m_SamplerLoc, 0);
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.4f;
GLUtils::setVec2(m_ProgramObj, "u_texSize", glm::vec2(m_RenderImages[0].width, m_RenderImages[0].height));
GLUtils::setFloat(m_ProgramObj, "u_needRotate", 1.0f); // u_needRotate == 1 开启形变
GLUtils::setFloat(m_ProgramObj, "u_rotateAngle", m_TransX * 1.5f);
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX / 2, m_TransY / 2, (float)screenW / screenH);
glUniformMatrix4fv(m_MVPMatLoc, 1, GL_FALSE, &m_MVPMatrix[0][0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
//2. 人像层的绘制
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[1]);
glUniform1i(m_SamplerLoc, 1);
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200 + 1));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.4f;
LOGCATE("AvatarSample::Draw() scaleLevel=%f", scaleLevel);
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX * 1.2f, m_TransY * 1.2f, (float)screenW / screenH);
GLUtils::setVec2(m_ProgramObj, "u_texSize", glm::vec2(m_RenderImages[0].width, m_RenderImages[0].height));
GLUtils::setFloat(m_ProgramObj, "u_needRotate", 0.0f);// u_needRotate == 0 关闭形变
GLUtils::setFloat(m_ProgramObj, "u_rotateAngle", m_TransX / 20);
glUniformMatrix4fv(m_MVPMatLoc, 1, GL_FALSE, &m_MVPMatrix[0][0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
//3. 外层的绘制
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
//切换另外一个着色器程序
glUseProgram(m_BlurProgramObj);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_TextureIds[2]);
GLUtils::setFloat(m_BlurProgramObj, "s_TextureMap", 0);
scaleLevel = static_cast<float>(1.0f + dScaleLevel * pow(-1, m_FrameIndex / 200));
scaleLevel = scaleLevel < 1.0 ? scaleLevel + 0.2f : scaleLevel;
m_ScaleY = m_ScaleX = scaleLevel + 0.8f;
UpdateMVPMatrix(m_MVPMatrix, m_AngleX, m_AngleY, m_TransX * 2.5f, m_TransY * 2.5f, (float)screenW / screenH);
GLUtils::setMat4(m_BlurProgramObj, "u_MVPMatrix", m_MVPMatrix);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
glDisable(GL_BLEND);
m_FrameIndex ++;
}
最终的 3D 阿凡达效果如下图所示。
手机晃动状态下的效果 手机静止状态下的效果
实现代码路径:
Android_OpenGLES_3_0
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