libgdx shaders- basic shader, but screen is blank

java, libgdx, opengl-es, shader

Solution

After looking at the code in `SpriteBatch` it seems that I had a few mistakes in my code. Below are the correct shaders:

default.vert:

attribute vec4 a_position;
attribute vec4 a_color;
attribute vec2 a_texCoord0;

uniform mat4 u_projTrans;

varying vec4 v_color;
varying vec2 v_texCoords;

void main() {
    v_color = a_color;
    v_texCoords = a_texCoord0;
    gl_Position = u_projTrans * a_position;
}

default.frag:

#ifdef GL_ES
    precision mediump float;
#endif

varying vec4 v_color;
varying vec2 v_texCoords;
uniform sampler2D u_texture;

void main() {
    gl_FragColor = v_color * texture2D(u_texture, v_texCoords);
}

Problem

I'm trying to understand shaders using libgdx, coming from an XNA/HLSL background. I'm trying to get a vert/frag shader pair to reproduce the output I get without a shader, but it's not displaying anything. Shader creation: ``` void SetupShader() { ShaderProgram.pedantic = false; shader = new ShaderProgram( Gdx.files.internal("assets/default.vert").readString(), Gdx.files.internal("assets/default.frag").readString()); if(!shader.isCompiled()) { Gdx.app.log("Problem loading shader:", shader.getLog()); } batch.setShader(shader); } ``` default.vert: ``` attribute vec4 a_Position; attribute vec4 a_Normal; attribute vec2 a_TexCoord; attribute vec4 a_Color; uniform mat4 u_projTrans; varying vec2 v_texCoords; varying vec4 v_color; void main() { v_color = a_Color; v_texCoords = a_TexCoord; gl_Position = u_projTrans * a_Position; } ``` default.frag: ``` #ifdef GL_ES precision mediump float; #endif varying vec2 v_texCoords; varying vec4 v_color; void main() { gl_FragColor = v_color; } ``` Rendering: ``` batch.begin(); for (GameObject gObj : gameObjects) gObj.Draw(batch); batch.end(); ``` Any suggestions here? I'm new to OpenGL-ES as well, so I may be missing something obvious. I looked around a bit before posting, and the doc for `SpriteBatch.setShader(ShaderProgram)` was as follows: Sets the shader to be used in a GLES 2.0 environment. Vertex position attribute is called "a_position", the texture coordinates attribute is called called "a_texCoords0", the color attribute is called "a_color". See ShaderProgram.POSITION_ATTRIBUTE, ShaderProgram.COLOR_ATTRIBUTE and ShaderProgram.TEXCOORD_ATTRIBUTE which gets "0" appened to indicate the use of the first texture unit. The projection matrix is uploaded via a mat4 uniform called "u_proj", the transform matrix is uploaded via a uniform called "u_trans", the combined transform and projection matrx is is uploaded via a mat4 uniform called "u_projTrans". The texture sampler is passed via a uniform called "u_texture". Call this method with a null argument to use the default shader.

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