[英]Implementing a fragment shader that uses a uniform Sampler2D (lwjgl)
我無法成功運行着色器,而且似乎缺少使它全部正常工作的步驟。 我最終遇到以下錯誤:
Exception in thread "main" org.lwjgl.opengl.OpenGLException: Invalid operation (1282)
at org.lwjgl.opengl.Util.checkGLError(Util.java:59)
at org.lwjgl.opengl.GL20.glUniform1i(GL20.java:374)
at sprites.Sprite.draw(Sprite.java:256)
at gui.Game.drawFrame(Game.java:238)
at gui.Game.gameLoop(Game.java:205)
at gui.Game.startGame(Game.java:244)
at tests.simple.SimpleShader.main(SimpleShader.java:36)
我的初始化始於:
int frag = FilterLoader.createShader("/tests/resources/shaders/grayscale.frag", GL20.GL_FRAGMENT_SHADER);
並且createShader方法如下所示:
int shader = GL20.glCreateShader(type);
if(shader == 0)
return 0;
StringBuilder code = new StringBuilder("");
String line;
try
{
String path = FilterLoader.class.getResource(filename).getPath();
BufferedReader reader = new BufferedReader(new FileReader(path));
while((line = reader.readLine()) != null)
{
code.append(line + "\n");
}
}
catch(Exception e)
{
e.printStackTrace();
System.err.println("Error reading in " + type + " shader");
return 0;
}
GL20.glShaderSource(shader, code);
GL20.glCompileShader(shader);
return shader;
然后,通過以下方式將着色器附加到特定的Sprite:
two.addFragmentShader(frag); //two is a Sprite
這只是簡單的:
fragmentShader = fragment_shader;
GL20.glAttachShader(shader, fragment_shader);
GL20.glLinkProgram(shader);
先前已在Sprites構造函數中使用以下方法初始化了int 着色器 :
shader = GL20.glCreateProgram();
這是以前的問題,但不再明顯。 現在,我將在Sprites(在本例中為兩個)draw方法中找到發生實際錯誤的位置,如下所示:
if(true)
{
GL20.glUseProgram(shader);
}
glPushMatrix();
glActiveTexture(GL13.GL_TEXTURE0);
imageData.getTexture().bind();
//The line below is where the error occurs.
GL20.glUniform1i(fragmentShader, GL13.GL_TEXTURE0);
int tx = (int)location.x;
int ty = (int)location.y;
glTranslatef(tx, ty, location.layer);
float texture_X = ((float)which_column/(float)columns);
float texture_Y = ((float)which_row/(float)rows);
float texture_XplusWidth = ((float)(which_column+wide)/(float)columns);
float texture_YplusHeight = ((float)(which_row+tall)/(float)rows);
glBegin(GL_QUADS);
{
GL11.glTexCoord2f(texture_X, texture_Y);
glVertex2f(0, 0);
GL11.glTexCoord2f(texture_X, texture_YplusHeight);
glVertex2f(0, getHeight());
GL11.glTexCoord2f(texture_XplusWidth, texture_YplusHeight);
glVertex2f(getWidth(), getHeight());
GL11.glTexCoord2f(texture_XplusWidth, texture_Y);
glVertex2f(getWidth(), 0);
}
glEnd();
GL20.glUseProgram(0);
glPopMatrix();
錯誤發生在這一行:
GL20.glUniform1i(fragmentShader, GL13.GL_TEXTURE0);
作為參考,我的着色器:
// simple fragment shader
uniform sampler2D texture;
void main()
{
vec4 color, texel;
color = gl_Color;
texel = texture2DRect(texture, gl_TexCoord[0].xy);
color *= texel;
float gray = dot(color.rgb, vec3(0.299, 0.587, 0.144));
gl_FragColor = vec4(gray, gray, gray, color.a);
}
我已經遍歷了教程,閱讀了有關錯誤的信息,但無法弄清楚錯過了哪些步驟。
GL20.glUniform1i(fragmentShader, GL13.GL_TEXTURE0);
這是錯的。 glUniform1i
的第一個參數是統一位置,您可以使用glGetUniformLocation
獲得該位置。
第二個參數是整數,但是對於紋理采樣器,您需要傳遞紋理單元號(0、1、2等),並將紋理綁定到該紋理單元,例如:
glUseProgram(program);
int loc = glGetUniformLocation(program, "texture");
glUniform1i(loc, 0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texId);
然后它應該工作。
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