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--- wiki2:oglpipeline [2015/11/21 08:02]
alfred [Transformaciones]
+++ wiki2:oglpipeline [2020/05/09 09:25] (actual)
@@ Línea 166: / Línea 166: @@
 ===== Color =====
+==== Define vertices, color and indexs ====
+<code java>
+float[] tableVerticesWithTriangles = {
+        // x, y          r,g,b
+, 0.5f,         1,0,0,
+        -0.5f,  0,       0,1,0,
+.5f,  0,        0,0,1
+};
-===== Transformaciones =====
+vertexData = ByteBuffer
+        .allocateDirect(tableVerticesWithTriangles.length * BYTES_PER_FLOAT)
+        .order(ByteOrder.nativeOrder())
+        .asFloatBuffer();
+vertexData.put(tableVerticesWithTriangles);
+byte[] tableIndices = {0, 1, 2};
+indexArray =  ByteBuffer.allocateDirect(3).put(tableIndices);
+</code>
+==== Shaders ====
+=== Vertex Shader ===
+<code>
+attribute vec4 a_Position;
+attribute vec4 a_Color;
+varying vec4 v_Color;
+void main()
+{
+    v_Color = a_Color;
+    gl_Position = a_Position;
+}
+</code>
+=== Fragment Shader ===
+<code>
+precision mediump float;
+varying vec4 v_Color;
+void main()
+{
+    gl_FragColor = v_Color;
+}
+</code>
+==== Render ====
+  * Obtain the attributes location for color and position.
+  * Write color and position (in this case this step could be performed only once).
+  * Enable them.
+  * Draw them.
+<code java>
+// next step is really important in java
+vertexData.position(0);
+indexArray.position(0);
+glClear(GL_COLOR_BUFFER_BIT);
+aColorLocation = glGetAttribLocation(program, A_COLOR);
+aPositionLocation = glGetAttribLocation(program, A_POSITION);
+glVertexAttribPointer(aPositionLocation, POSITION_COMPONENT_COUNT, GL_FLOAT,
+        false, STRIDE, vertexData);
+glEnableVertexAttribArray(aPositionLocation);
+vertexData.position(POSITION_COMPONENT_COUNT);
+glVertexAttribPointer(aColorLocation, COLOR_COMPONENT_COUNT, GL_FLOAT,
+        false, STRIDE, vertexData);
+glEnableVertexAttribArray(aColorLocation);
+glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_BYTE, indexArray);
+glDisableVertexAttribArray(aPositionLocation);
+glDisableVertexAttribArray(aColorLocation);
+</code>
+=== Constant values ===
+<code java>
+private static final int BYTES_PER_FLOAT = 4;
+private static final int POSITION_COMPONENT_COUNT = 2;
+private static final int COLOR_COMPONENT_COUNT = 3;
+private static final int STRIDE = (POSITION_COMPONENT_COUNT + COLOR_COMPONENT_COUNT) * BYTES_PER_FLOAT;
+</code>
+==== Example ====
+{{:wiki2:ogl:color.zip|Example}}
+===== Transformaciones y proyecciones =====
+  * {{:wiki2:ogl:tutorial_3_matrices.pdf|Explicacion de matrices y proyecciones}}
+  * {{:wiki2:ogl:objectoriented.matrix.zip|Ejemplo de matrices y orientación a objetos en OpenGL ES}}
 ===== Texturas =====
+==== Cargar texturas ====
+  - Read the texture.
+  - Bind the texture.
+  - Set filtering: a default must be set, or the texture will be black.
+  - Load the bitmap into the bound texture with ''texImage2D''.
+  - Unbind from the texture with ''glBindTexture(GL_TEXTURE_2D, 0)''.
+<code java>
+public static int loadTexture(Context context, int resourceId) {
+    final int[] textureObjectIds = new int[1];
+    glGenTextures(1, textureObjectIds, 0);
+    if (textureObjectIds[0] == 0) {
+        Log.w(TAG, "Could not generate a new OpenGL texture object.");
+        return 0;
+    }
+    final BitmapFactory.Options options = new BitmapFactory.Options();
+    options.inScaled = false;
+    final Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), resourceId, options);
+    if (bitmap == null) {
+        Log.w(TAG, "Resource ID " + resourceId + " could not be decoded.");
+        glDeleteTextures(1, textureObjectIds, 0);
+        return 0;
+    }
+    glBindTexture(GL_TEXTURE_2D, textureObjectIds[0]);
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
+    texImage2D(GL_TEXTURE_2D, 0, bitmap, 0);
+    glBindTexture(GL_TEXTURE_2D, 0);
+    bitmap.recycle();
+    Log.w(TAG, "Texture loaded");
+    return textureObjectIds[0];
+}
+</code>
+Podríamos cargar mipmaps:
+<code java>
+glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+glGenerateMipmap(GL_TEXTURE_2D);
+</code>
+==== Shaders ====
+=== Vertex ===
+<code>
+attribute vec4 a_Position;
+attribute vec2 a_TextureCoordinates;
+varying vec2 v_TextureCoordinates;
+void main()
+{
+    v_TextureCoordinates = a_TextureCoordinates;
+    gl_Position = a_Position;
+}
+</code>
+=== Fragment ===
+<code>
+precision mediump float;
+uniform sampler2D u_TextureUnit;
+varying vec2 v_TextureCoordinates;
+void main()
+{
+    gl_FragColor = texture2D(u_TextureUnit, v_TextureCoordinates);
+}
+</code>
+==== When render ====
+<code java>
+vertexData.position(0);
+indexArray.position(0);
+glClear(GL_COLOR_BUFFER_BIT);
+glVertexAttribPointer(aPositionLocation, POSITION_COMPONENT_COUNT, GL_FLOAT,
+        false, STRIDE, vertexData);
+vertexData.position(POSITION_COMPONENT_COUNT);
+glVertexAttribPointer(aTextCoordLocation, TEXTURE_COORDINATES_COMPONENT_COUNT, GL_FLOAT,
+        false, STRIDE, vertexData);
+glEnableVertexAttribArray(aPositionLocation);
+glEnableVertexAttribArray(aTextCoordLocation);
+glActiveTexture(GL_TEXTURE0);
+glBindTexture(GL_TEXTURE_2D, texture);
+glUniform1i(uTextureUnitLocation, 0);
+glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_BYTE, indexArray);
+glDisableVertexAttribArray(aPositionLocation);
+glDisableVertexAttribArray(aTextCoordLocation);
+</code>
+Setting these values:
+<code java>
+float[] tableVerticesWithTriangles = {
+        // x, y          s,t
+, 0.5f,         0.5f,0,
+        -0.5f,  0,       0,1,
+.5f,  0,        1,1
+};
+</code>
+And these constants:
+<code java>
+private static final int BYTES_PER_FLOAT = 4;
+private static final int POSITION_COMPONENT_COUNT = 2;
+private static final int TEXTURE_COORDINATES_COMPONENT_COUNT = 2;
+private static final int STRIDE = (POSITION_COMPONENT_COUNT + TEXTURE_COORDINATES_COMPONENT_COUNT) * BYTES_PER_FLOAT;
+</code>
+==== Code ====
+  * {{:wiki2:ogl:textures.zip|}}
 ===== Luces =====

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