OpenGL ES-＞GLSurfaceView进行点、线段、三角形等基本图元的绘制

GLSurfaceView代码见OpenGL ES-＞顶点着色器和片段着色器代码，只修改顶点数组，片段着色器的颜色，和绘制方式进行不同图元绘制

绘制点

• GL_POINTS方式

// 顶点数据
val vertices = floatArrayOf(
    0.8f, -0.8f, 0.0f,
    -0.8f, -0.8f, 0.0f,
    0.0f, 0.8f, 0.0f,
)

// 顶点着色器代码
val vertexShaderCode = """#version 300 es
                        layout (location = 0) in vec4 aPosition;
                        
                        void main() {
                          gl_Position = aPosition;
                          
                        }""".trimIndent()
                        
// 片段着色器代码
val fragmentShaderCode = """#version 300 es
        precision mediump float;
        uniform vec4 vColor;
        out vec4 fragColor;
        
        void main() {
          fragColor = vColor;
        }""".trimIndent()

// 获得顶点数据
val positionHandle = GLES30.glGetAttribLocation(program, "aPosition")
GLES30.glEnableVertexAttribArray(positionHandle)
GLES30.glVertexAttribPointer(positionHandle, 3, GLES30.GL_FLOAT, false, 0, 0)

// 设置片段着色器的颜色
val colorHandle = GLES30.glGetUniformLocation(program, "vColor")
GLES30.glUniform4f(colorHandle, 1.0f,0.5f,0.5f,1.0f)
// 绘制
GLES30.glDrawArrays(GL_POINTS, 0, 3)

// 禁用顶点数据
GLES30.glDisableVertexAttribArray(positionHandle)

绘制线段

• GL_LINES方式

// 顶点数据
val vertices = floatArrayOf(
    0.5f, 0.5f, 0.0f,
    -0.5f, 0.5f, 0.0f,
    -0.5f, -0.5f, 0.0f,
    0.5f, -0.5f, 0.0f,
)

// 顶点着色器代码
val vertexShaderCode = """#version 300 es
                        layout (location = 0) in vec4 aPosition;
                        
                        void main() {
                          gl_Position = aPosition;
                          
                        }""".trimIndent()
                        
// 片段着色器代码
val fragmentShaderCode = """#version 300 es
        precision mediump float;
        uniform vec4 vColor;
        out vec4 fragColor;
        
        void main() {
          fragColor = vColor;
        }""".trimIndent()

// 获得顶点数据
val positionHandle = GLES30.glGetAttribLocation(program, "aPosition")
GLES30.glEnableVertexAttribArray(positionHandle)
GLES30.glVertexAttribPointer(positionHandle, 3, GLES30.GL_FLOAT, false, 0, 0)

// 设置片段着色器的颜色
val colorHandle = GLES30.glGetUniformLocation(program, "vColor")
GLES30.glUniform4f(colorHandle, 1.0f,0.5f,0.5f,1.0f)
GLES30.glLineWidth(20f) // 设置线条宽度，否则看不到线条
// 绘制
GLES30.glDrawArrays(GL_LINES, 0, 4)

// 禁用顶点数据
GLES30.glDisableVertexAttribArray(positionHandle)

• GL_LINE_STRIP方式

// 顶点数据
val vertices = floatArrayOf(
    0.5f, 0.5f, 0.0f,
    -0.5f, 0.5f, 0.0f,
    -0.5f, -0.5f, 0.0f,
    0.5f, -0.5f, 0.0f,
)

// 顶点着色器代码
val vertexShaderCode = """#version 300 es
                        layout (location = 0) in vec4 aPosition;
                        
                        void main() {
                          gl_Position = aPosition;
                          
                        }""".trimIndent()
                        
// 片段着色器代码
val fragmentShaderCode = """#version 300 es
        precision mediump float;
        uniform vec4 vColor;
        out vec4 fragColor;
        
        void main() {
          fragColor = vColor;
        }""".trimIndent()

// 获得顶点数据
val positionHandle = GLES30.glGetAttribLocation(program, "aPosition")
GLES30.glEnableVertexAttribArray(positionHandle)
GLES30.glVertexAttribPointer(positionHandle, 3, GLES30.GL_FLOAT, false, 0, 0)

// 设置片段着色器的颜色
val colorHandle = GLES30.glGetUniformLocation(program, "vColor")
GLES30.glUniform4f(colorHandle, 1.0f,0.5f,0.5f,1.0f)
GLES30.glLineWidth(20f) // 设置线条宽度，否则看不到线条
// 绘制
GLES30.glDrawArrays(GL_LINE_STRIP, 0, 4)

// 禁用顶点数据
GLES30.glDisableVertexAttribArray(positionHandle)

• GL_LINE_LOOP方式

// 顶点数据
val vertices = floatArrayOf(
    0.5f, 0.5f, 0.0f,
    -0.5f, 0.5f, 0.0f,
    -0.5f, -0.5f, 0.0f,
    0.5f, -0.5f, 0.0f,
)

// 顶点着色器代码
val vertexShaderCode = """#version 300 es
                        layout (location = 0) in vec4 aPosition;
                        
                        void main() {
                          gl_Position = aPosition;
                          
                        }""".trimIndent()
                        
// 片段着色器代码
val fragmentShaderCode = """#version 300 es
        precision mediump float;
        uniform vec4 vColor;
        out vec4 fragColor;
        
        void main() {
          fragColor = vColor;
        }""".trimIndent()

// 获得顶点数据
val positionHandle = GLES30.glGetAttribLocation(program, "aPosition")
GLES30.glEnableVertexAttribArray(positionHandle)
GLES30.glVertexAttribPointer(positionHandle, 3, GLES30.GL_FLOAT, false, 0, 0)

// 设置片段着色器的颜色
val colorHandle = GLES30.glGetUniformLocation(program, "vColor")
GLES30.glUniform4f(colorHandle, 1.0f,0.5f,0.5f,1.0f)
GLES30.glLineWidth(20f) // 设置线条宽度，否则看不到线条
// 绘制
GLES30.glDrawArrays(GL_LINE_LOOP, 0, 4)

// 禁用顶点数据
GLES30.glDisableVertexAttribArray(positionHandle)

绘制三角形

• GL_TRIANGLES方式

// 顶点数据
val vertices = floatArrayOf(
      0.5f, 0f, 0.0f,
      0f, 0.5f, 0.0f,
     -0.5f, 0f, 0.0f,

     -0.6f, 0f, 0.0f,
     0f, -0.6f, 0.0f,
     0.6f, 0f, 0.0f,
)

// 顶点着色器代码
val vertexShaderCode = """#version 300 es
                        layout (location = 0) in vec4 aPosition;
                        
                        void main() {
                          gl_Position = aPosition;
                          
                        }""".trimIndent()
                        
// 片段着色器代码
val fragmentShaderCode = """#version 300 es
        precision mediump float;
        uniform vec4 vColor;
        out vec4 fragColor;
        
        void main() {
          fragColor = vColor;
        }""".trimIndent()

// 获得顶点数据
val positionHandle = GLES30.glGetAttribLocation(program, "aPosition")
GLES30.glEnableVertexAttribArray(positionHandle)
GLES30.glVertexAttribPointer(positionHandle, 3, GLES30.GL_FLOAT, false, 0, 0)

// 设置片段着色器的颜色
val colorHandle = GLES30.glGetUniformLocation(program, "vColor")
GLES30.glUniform4f(colorHandle, 1.0f,0.5f,0.5f,1.0f)
GLES30.glLineWidth(20f) // 设置线条宽度，否则看不到线条
// 绘制
GLES30.glDrawArrays(GL_TRIANGLES, 0, 6)

// 禁用顶点数据
GLES30.glDisableVertexAttribArray(positionHandle)