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Cover image for WebGL month. Day 21. Rendering a minecraft terrain

WebGL month. Day 21. Rendering a minecraft terrain

lesnitsky profile image Andrei Lesnitsky ・4 min read

This is a series of blog posts related to WebGL. New post will be available every day

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Hey 👋

Welcome to WebGL month.

Yesterday we rendered a single minecraft dirt cube, let's render a terrain today!

We'll need to store each block position in separate transform matrix

📄 src/3d-textured.js


  gl.viewport(0, 0, canvas.width, canvas.height);

+ const matrices = [];
+ 
  function frame() {
      mat4.rotateY(cube.modelMatrix, cube.modelMatrix, Math.PI / 180);


Now let's create 10k blocks iteration over x and z axis from -50 to 50

📄 src/3d-textured.js


  const matrices = [];

+ for (let i = -50; i < 50; i++) {
+     for (let j = -50; j < 50; j++) {
+         const matrix = mat4.create();
+     }
+ }
+ 
  function frame() {
      mat4.rotateY(cube.modelMatrix, cube.modelMatrix, Math.PI / 180);


Each block is a size of 2 (vertex coordinates are in [-1..1] range) so positions should be divisible by two

📄 src/3d-textured.js

  for (let i = -50; i < 50; i++) {
      for (let j = -50; j < 50; j++) {
          const matrix = mat4.create();
+ 
+         const position = [i * 2, (Math.floor(Math.random() * 2) - 1) * 2, j * 2];
      }
  }


Now we need to create a transform matrix. Let's use ma4.fromTranslation

📄 src/3d-textured.js

          const matrix = mat4.create();

          const position = [i * 2, (Math.floor(Math.random() * 2) - 1) * 2, j * 2];
+         mat4.fromTranslation(matrix, position);
      }
  }


Let's also rotate each block around Y axis to make terrain look more random

📄 src/3d-textured.js

  gl.viewport(0, 0, canvas.width, canvas.height);

  const matrices = [];
+ const rotationMatrix = mat4.create();

  for (let i = -50; i < 50; i++) {
      for (let j = -50; j < 50; j++) {

          const position = [i * 2, (Math.floor(Math.random() * 2) - 1) * 2, j * 2];
          mat4.fromTranslation(matrix, position);
+ 
+         mat4.fromRotation(rotationMatrix, Math.PI * Math.round(Math.random() * 4), [0, 1, 0]);
+         mat4.multiply(matrix, matrix, rotationMatrix);
      }
  }


and finally push matrix of each block to matrices collection

📄 src/3d-textured.js


          mat4.fromRotation(rotationMatrix, Math.PI * Math.round(Math.random() * 4), [0, 1, 0]);
          mat4.multiply(matrix, matrix, rotationMatrix);
+ 
+         matrices.push(matrix);
      }
  }


Since our blocks are static, we don't need a rotation transform in each frame

📄 src/3d-textured.js

  }

  function frame() {
-     mat4.rotateY(cube.modelMatrix, cube.modelMatrix, Math.PI / 180);
- 
      gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, cube.modelMatrix);
      gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, cube.normalMatrix);


Now we'll need to iterate over matrices collection and issue a draw call for each cube with its transform matrix passed to uniform

📄 src/3d-textured.js

  }

  function frame() {
-     gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, cube.modelMatrix);
-     gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, cube.normalMatrix);
+     matrices.forEach((matrix) => {
+         gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, matrix);
+         gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, cube.normalMatrix);

-     gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3);
+         gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3);
+     });

      requestAnimationFrame(frame);
  }

Now let's create an animation of rotating camera. Camera has a position and a point where it is pointed. So to implement this, we need to rotate focus point around camera position. Let's first get rid of static view matrix

📄 src/3d-textured.js

  const viewMatrix = mat4.create();
  const projectionMatrix = mat4.create();

- mat4.lookAt(viewMatrix, [0, 4, -7], [0, 0, 0], [0, 1, 0]);
- 
  mat4.perspective(projectionMatrix, (Math.PI / 360) * 90, canvas.width / canvas.height, 0.01, 100);

  gl.uniformMatrix4fv(programInfo.uniformLocations.viewMatrix, false, viewMatrix);

Define camera position, camera focus point vector and focus point transform matrix

📄 src/3d-textured.js

- import { mat4 } from 'gl-matrix';
+ import { mat4, vec3 } from 'gl-matrix';

  import vShaderSource from './shaders/3d-textured.v.glsl';
  import fShaderSource from './shaders/3d-textured.f.glsl';
      }
  }

+ const cameraPosition = [0, 10, 0];
+ const cameraFocusPoint = vec3.fromValues(30, 0, 0);
+ const cameraFocusPointMatrix = mat4.create();
+ 
+ mat4.fromTranslation(cameraFocusPointMatrix, cameraFocusPoint);
+ 
  function frame() {
      matrices.forEach((matrix) => {
          gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, matrix);

Our camera is located in 0.0.0, so we need to translate camera focus point to 0.0.0, rotate it, and translate back to original position

📄 src/3d-textured.js

  mat4.fromTranslation(cameraFocusPointMatrix, cameraFocusPoint);

  function frame() {
+     mat4.translate(cameraFocusPointMatrix, cameraFocusPointMatrix, [-30, 0, 0]);
+     mat4.rotateY(cameraFocusPointMatrix, cameraFocusPointMatrix, Math.PI / 360);
+     mat4.translate(cameraFocusPointMatrix, cameraFocusPointMatrix, [30, 0, 0]);
+ 
      matrices.forEach((matrix) => {
          gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, matrix);
          gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, cube.normalMatrix);

Final step – update view matrix uniform

📄 src/3d-textured.js

      mat4.rotateY(cameraFocusPointMatrix, cameraFocusPointMatrix, Math.PI / 360);
      mat4.translate(cameraFocusPointMatrix, cameraFocusPointMatrix, [30, 0, 0]);

+     mat4.getTranslation(cameraFocusPoint, cameraFocusPointMatrix);
+ 
+     mat4.lookAt(viewMatrix, cameraPosition, cameraFocusPoint, [0, 1, 0]);
+     gl.uniformMatrix4fv(programInfo.uniformLocations.viewMatrix, false, viewMatrix);
+ 
      matrices.forEach((matrix) => {
          gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, matrix);
-         gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, cube.normalMatrix);

          gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3);
      });

That's it!

This approach is not very performant though, as we're issuing 2 gl calls for each object, so it is a 20k of gl calls each frame. GL calls are expensive, so we'll need to reduce this number. We'll learn a great technique tomorrow!


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