我正在做一个简单的 OpenGL 4 项目。我要做的就是改变鼠标指针周围的 alpha 值并混合。经过一些工作,我设法得到一个圆圈来更改值,但它是静态的(不随鼠标移动)并且以(0,512)为中心,非常不是我的鼠标位置。我通过passiveMotionFunc发送鼠标值:
void
motion ( int x, int y)
{
MousePos.x = x;
MousePos.y = y;
printf("x=%i\ny=%i\n\n", x, y);
glUniform2fv(glGetUniformLocation(program, "MousePos"), 2, MousePos);
glutPostRedisplay();
}
MousePos 只是一个简单的浮动容器。我有打印语句,所以我可以看到我的鼠标位置的值。
我的碎片着色器很简单:
in vec4 color;
in vec4 vPosition;
in vec2 MousePos;
out vec4 fColor;
void
main()
{
//float x = gl_FragCoord.X;
//float y = gl_FragCoord.Y;
float distance = sqrt(pow(MousePos.x-gl_FragCoord.x, 2) + pow(MousePos.y-gl_FragCoord.y, 2));
if(distance > 30)
fColor = color;
else{
float a = .1;
fColor = color;
fColor.a = a;
}
}
我完全坚持这一点。我假设碎片着色器没有得到更新的鼠标坐标,因为如果 FragCoord 被搞砸了,它就不会产生一个圆圈。
编辑:我在 main() 中的 glutDisplay 和 glutPassiveFunc 之前的 init() 函数中设置了我的混合。
void
init()
{
wall();
redwall();
// Create a vertex array object
GLuint vao;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
// Create and initialize a buffer object
GLuint buffer;
glGenBuffers( 1, &buffer );
glBindBuffer( GL_ARRAY_BUFFER, buffer );
glBufferData( GL_ARRAY_BUFFER, sizeof(points) + sizeof(quad_colors), NULL, GL_STATIC_DRAW );
glBufferSubData( GL_ARRAY_BUFFER, 0, sizeof(points), points );
glBufferSubData( GL_ARRAY_BUFFER, sizeof(points), sizeof(quad_colors), quad_colors );
// Load shaders and use the resulting shader program
program = InitShader( "p6v.glsl", "p6f.glsl" );
glUseProgram( program );
// set up vertex arrays
GLuint vPosition = glGetAttribLocation( program, "vPosition" );
glEnableVertexAttribArray( vPosition );
glVertexAttribPointer( vPosition, 4, GL_FLOAT, GL_FALSE, 0,
BUFFER_OFFSET(0) );
GLuint vColor = glGetAttribLocation( program, "vColor" );
glEnableVertexAttribArray( vColor );
glVertexAttribPointer( vColor, 4, GL_FLOAT, GL_FALSE, 0,
BUFFER_OFFSET(sizeof(points)) );
//glEnable(GL_DEPTH_TEST);
glEnable( GL_BLEND );
glEnable( GL_ALPHA_TEST);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDepthMask(false);
glClearColor( 0.0, 0.5, 1.0, 1.0 );
}
EDIT2:这是我的 vec2 定义:
struct vec2 {
GLfloat x;
GLfloat y;
//
// --- Constructors and Destructors ---
//
vec2( GLfloat s = GLfloat(0.0) ) :
x(s), y(s) {}
vec2( GLfloat x, GLfloat y ) :
x(x), y(y) {}
vec2( const vec2& v )
{ x = v.x; y = v.y; }
//
// --- Indexing Operator ---
//
GLfloat& operator [] ( int i ) { return *(&x + i); }
const GLfloat operator [] ( int i ) const { return *(&x + i); }
//
// --- (non-modifying) Arithematic Operators ---
//
vec2 operator - () const // unary minus operator
{ return vec2( -x, -y ); }
vec2 operator + ( const vec2& v ) const
{ return vec2( x + v.x, y + v.y ); }
vec2 operator - ( const vec2& v ) const
{ return vec2( x - v.x, y - v.y ); }
vec2 operator * ( const GLfloat s ) const
{ return vec2( s*x, s*y ); }
vec2 operator * ( const vec2& v ) const
{ return vec2( x*v.x, y*v.y ); }
friend vec2 operator * ( const GLfloat s, const vec2& v )
{ return v * s; }
vec2 operator / ( const GLfloat s ) const {
#ifdef DEBUG
if ( std::fabs(s) < DivideByZeroTolerance ) {
std::cerr << "[" << __FILE__ << ":" << __LINE__ << "] "
<< "Division by zero" << std::endl;
return vec2();
}
#endif // DEBUG
GLfloat r = GLfloat(1.0) / s;
return *this * r;
}
//
// --- (modifying) Arithematic Operators ---
//
vec2& operator += ( const vec2& v )
{ x += v.x; y += v.y; return *this; }
vec2& operator -= ( const vec2& v )
{ x -= v.x; y -= v.y; return *this; }
vec2& operator *= ( const GLfloat s )
{ x *= s; y *= s; return *this; }
vec2& operator *= ( const vec2& v )
{ x *= v.x; y *= v.y; return *this; }
vec2& operator /= ( const GLfloat s ) {
#ifdef DEBUG
if ( std::fabs(s) < DivideByZeroTolerance ) {
std::cerr << "[" << __FILE__ << ":" << __LINE__ << "] "
<< "Division by zero" << std::endl;
}
#endif // DEBUG
GLfloat r = GLfloat(1.0) / s;
*this *= r;
return *this;
}
//
// --- Insertion and Extraction Operators ---
//
friend std::ostream& operator << ( std::ostream& os, const vec2& v ) {
return os << "( " << v.x << ", " << v.y << " )";
}
friend std::istream& operator >> ( std::istream& is, vec2& v )
{ return is >> v.x >> v.y ; }
//
// --- Conversion Operators ---
//
operator const GLfloat* () const
{ return static_cast<const GLfloat*>( &x ); }
operator GLfloat* ()
{ return static_cast<GLfloat*>( &x ); }
};