OpenGL ES 2.0 Practice 4 : Simple Light

OpenGL ES 2.0 Practice 4 : Simple Light

3차원 공간에서 Triangle 표면에 라이팅(Lighting) 처리를 통해 보다 실질적인 효과를 나타내게 합니다.

Lighting 처리는 Light 의 감도 조절을 위해 각각의 Vertex(position)에 대한 Normal (법선벡터) 과 Light Direction 을 이용하며, 색상은 Light Color 와 Triangle 의 색상을 의미하는 Material Diffuser 값으로 연산합니다.

Lighting 원리에 대해서는 http://www.opengl-tutorial.org/beginners-tutorials/tutorial-8-basic-shading/ 를 참조 하세요..

   "precision mediump float;\n" +

                    "attribute vec3 aPosition;\n" +

                    "attribute vec3 aNormal;\n" +

                    "uniform mat4 uProjMatrix;\n" +

                    "uniform mat4 uViewMatrix;\n" +

                    "uniform mat4 uModelMatrix;\n" +

                    "uniform vec3 uLightColor;\n" +

                    "uniform vec3 uLightDir;\n" +

                    "uniform vec3 uMaterialDiffuse;\n" +

                    "varying vec3 vColor;\n" +

                    "void main() {\n" +

                    " gl_Position = uProjMatrix * uViewMatrix * uModelMatrix * vec4(aPosition, 1.0);\n" +

                    "   vec3 normal_cameraspace = (uViewMatrix * uModelMatrix * vec4(aNormal, 1.0)).xyz;\n" +

                    "   vec3 lightdir_cameraspace = (uViewMatrix * vec4(uLightDir, 1.0)).xyz;" +

                    "   vec3 n = normalize(normal_cameraspace);\n" +

                    "   vec3 l = normalize(lightdir_cameraspace);\n" +

                    "   float cosTheta = clamp( dot(n, l), 0.0, 1.0);" +

                    "   vColor = uMaterialDiffuse * uLightColor * cosTheta;" +

                    "}\n"

여기서는 태양광 같은 방향만 가지는 Directional Lighting 개념으로 구현 하였습니다. 

그리고 View Matrix와 Model Matrix 를 분리하여 물체(Triangle) 만 회전되도록 구현 하였습니다. (즉, Lighting 방향을 고정하고 물체만 회전)

다음 코드는 attribute 및 uniform 변수를 설정하는 코드 입니다. 

int aPositionLoc = GLES20.glGetAttribLocation(mProgram, "aPosition");

        GLES20.glVertexAttribPointer(aPositionLoc, 3, GLES20.GL_FLOAT, false, 0, mPosition);

        int aNormalLoc = GLES20.glGetAttribLocation(mProgram, "aNormal");

        GLES20.glVertexAttribPointer(aNormalLoc, 3, GLES20.GL_FLOAT, false, 0, mNormal);

        // light color

        GLES20.glUniform3f(GLES20.glGetUniformLocation(mProgram, "uLightColor"), 1.0f, 1.0f, 1.0f);

        // triangle material color

        GLES20.glUniform3f(GLES20.glGetUniformLocation(mProgram, "uMaterialDiffuse"), 0.2f, 0.7f, 0.3f);

        // light dir

        GLES20.glUniform3f(GLES20.glGetUniformLocation(mProgram, "uLightDir"), 1.0f, -1.0f, -1.0f);

        // triangle model matrix

        // no transform (identity matrix)

        // y-axis, 1 degree rotation every frames

        Matrix.rotateM(mModelMatrix, 0, 1.0f, 0.0f, 1.0f, 0.0f);

        GLES20.glUniformMatrix4fv(GLES20.glGetUniformLocation(mProgram, "uModelMatrix"), 1, false, mModelMatrix, 0);

        // view matrix

        GLES20.glUniformMatrix4fv(GLES20.glGetUniformLocation(mProgram, "uViewMatrix"), 1, false, mViewMatrix, 0);

        // projection matrix

        GLES20.glUniformMatrix4fv(GLES20.glGetUniformLocation(mProgram, "uProjMatrix"), 1, false, mProjMatrix, 0);

        GLES20.glEnableVertexAttribArray(aPositionLoc);

        GLES20.glEnableVertexAttribArray(aNormalLoc);

결과 화면... (Neuxs 7 2nd, Android 6.0)

OpenGLES20SimpleLight.zip