I'm trying to render font on screen using freetype. For that, I implemented single channel texture but it always samples 0.
cpp
unsigned char *blankData = new unsigned char[8 * 8];
for(int i = 0; i < 8 * 8; i++){
blankData[i] = 126;
}
glActiveTexture(GL_TEXTURE0);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
GLuint m_texture2D;
glGenTextures(1, &m_texture2D);
glBindTexture(GL_TEXTURE_2D, m_texture2D);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, 8, 8, 0, GL_RED, GL_UNSIGNED_BYTE, blankData);
glUniform1i(glGetUniformLocation(m_program, "texture2D"), 0);
checkGLError();
glGetError()
returns GL_NO_ERROR
fragment Shader
#version 330 core
in vec2 texCoord;
in vec4 color;
uniform sampler2D texture2D;
out vec4 outColor;
void main()
{
vec4 texColor = texture(texture2D, texCoord);
outColor = vec4(texColor.r, texColor.r, texColor.r, 1.0f);
}
ff00ff: clear color
black: fragment shader output texcoord bottomLeft(0, 0) to topRight(1, 1)
If you are not generating mipmaps (with glGenerateMipmap
) it is important to set GL_TEXTURE_MIN_FILTER
. Since the default filter is GL_NEAREST_MIPMAP_LINEAR
, the texture would be "Mipmap Incomplete" if you do not change the minimize function to GL_NEAREST
or GL_LINEAR
.
glBindTexture(GL_TEXTURE_2D, m_texture2D);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);