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◆ main openmsx / src / video / gl_transform.hh
6.5 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
#ifndef GL_TRANSFORM_HH
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#define GL_TRANSFORM_HH
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// openGL ES 2.0 removed functions like
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//   glRotate(), glTranslate(), glScale(), ...
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// This code can be used to replace them.
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//
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// This code was inspired by the 'glm' library (though written from scratch).
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// Compared to glm this code is much simpler but offers much less functionality.
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//   http://glm.g-truc.net
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#include "gl_mat.hh"
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#include "gl_vec.hh"
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namespace gl {
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// Returns a 4x4 scaling matrix for the given xyz scale factors.
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// Comparable to the glScale() function.
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[[nodiscard]] constexpr mat4 scale(const vec3& xyz)
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{
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	return mat4(vec4(xyz, 1.0f));
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}
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// Multiplies the given matrix by a scaling matrix. Equivalent to (but more
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// efficient than) 'A * scale(xyz)'.
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[[nodiscard]] constexpr mat4 scale(const mat4& A, const vec3& xyz)
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{
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	return {A[0] * xyz.x,
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	        A[1] * xyz.y,
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	        A[2] * xyz.z,
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	        A[3]};
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}
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// Returns a 4x4 translation matrix for the given xyz translation vector.
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// Comparable to the glTranslate() function.
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[[nodiscard]] constexpr mat4 translate(const vec3& xyz)
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{
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	mat4 result;
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	result[3] = vec4(xyz, 1.0f);
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	return result;
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}
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// Multiplies the given matrix by a translation matrix. Equivalent to (but
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// more efficient than) 'A * translate(xyz)'.
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[[nodiscard]] constexpr mat4 translate(mat4& A, const vec3& xyz)
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{
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	return {A[0],
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	        A[1],
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	        A[2],
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	        A[0] * xyz.x + A[1] * xyz.y + A[2] * xyz.z + A[3]};
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}
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// Returns a 4x4 rotation matrix for rotation of the given 'angle' around the
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// 'xyz' axis.
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// Comparable to the glRotate() function, but with these differences:
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//  - 'angle' is in radians instead of degrees
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//  - 'axis' must be a normalized vector
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[[nodiscard]] inline mat4 rotate(float angle, const vec3& axis)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	vec3 temp = (1.0f - c) * axis;
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	return {vec4(axis.x * temp.x + c,
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	             axis.y * temp.x + s * axis.z,
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	             axis.z * temp.x - s * axis.y,
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	             0.0f),
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	        vec4(axis.x * temp.y - s * axis.z,
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	             axis.y * temp.y + c,
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	             axis.z * temp.y + s * axis.x,
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	             0.0f),
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	        vec4(axis.x * temp.z + s * axis.y,
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	             axis.y * temp.z - s * axis.x,
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	             axis.z * temp.z + c,
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	             0.0f),
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	        vec4(0.0f,
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	             0.0f,
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	             0.0f,
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	             1.0f)};
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}
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// Multiplies the given matrix by a rotation matrix. Equivalent to
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// 'A * rotate(angle, axis)'.
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[[nodiscard]] inline mat4 rotate(const mat4& A, float angle, const vec3& axis)
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{
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	// TODO this could be optimized (only a little), though it's rarely used
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	return A * rotate(angle, axis);
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}
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// Returns a 4x4 rotation matrix for rotation around the X-axis. Much more
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// efficient than calling the generic rotate() function with a vec3(1,0,0)
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// axis.
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[[nodiscard]] inline mat4 rotateX(float angle)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	return {vec4(1.0f, 0.0f, 0.0f, 0.0f),
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	        vec4(0.0f,  c  ,  s  , 0.0f),
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	        vec4(0.0f, -s  ,  c  , 0.0f),
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	        vec4(0.0f, 0.0f, 0.0f, 1.0f)};
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}
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// Multiplies the given matrix by a X-rotation matrix. Equivalent to (but more
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// efficient than) 'A * rotateX(angle)'.
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[[nodiscard]] inline mat4 rotateX(const mat4& A, float angle)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	return {A[0],
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	        A[1] * c + A[2] * s,
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	        A[2] * c - A[1] * s,
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	        A[3]};
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}
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// Returns a 4x4 rotation matrix for rotation around the Y-axis. Much more
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// efficient than calling the generic rotate() function with a vec3(0,1,0)
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// axis.
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[[nodiscard]] inline mat4 rotateY(float angle)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	return {vec4( c  , 0.0f, -s  , 0.0f),
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	        vec4(0.0f, 1.0f, 0.0f, 0.0f),
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	        vec4( s  , 0.0f,  c  , 0.0f),
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	        vec4(0.0f, 0.0f, 0.0f, 1.0f)};
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}
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// Multiplies the given matrix by a Y-rotation matrix. Equivalent to (but more
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// efficient than) 'A * rotateY(angle)'.
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[[nodiscard]] inline mat4 rotateY(const mat4& A, float angle)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	return {A[0] * c - A[2] * s,
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	        A[1],
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	        A[2] * c + A[0] * s,
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	        A[3]};
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}
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// Returns a 4x4 rotation matrix for rotation around the Z-axis. Much more
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// efficient than calling the generic rotate() function with a vec3(0,0,1)
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// axis.
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[[nodiscard]] inline mat4 rotateZ(float angle)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	return {vec4( c  ,  s  , 0.0f, 0.0f),
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	        vec4(-s  ,  c  , 0.0f, 0.0f),
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	        vec4(0.0f, 0.0f, 1.0f, 0.0f),
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	        vec4(0.0f, 0.0f, 0.0f, 1.0f)};
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}
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// Multiplies the given matrix by a Z-rotation matrix. Equivalent to (but more
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// efficient than) 'A * rotateZ(angle)'.
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[[nodiscard]] inline mat4 rotateZ(const mat4& A, float angle)
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{
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	float s = sinf(angle);
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	float c = cosf(angle);
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	return {A[0] * c + A[1] * s,
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	        A[1] * c - A[0] * s,
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	        A[2],
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	        A[3]};
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}
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// Note: Don't use "near" or "far" as names since those are macros on Windows.
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// Returns a 4x4 orthographic projection matrix. Comparable to
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// the glOrtho() function.
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[[nodiscard]] constexpr mat4 ortho(
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	float left,    float right,
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	float bottom,  float top,
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	float nearVal, float farVal)
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{
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	return {vec4(-2.0f / (left - right),  0.0f, 0.0f, 0.0f),
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	        vec4( 0.0f, -2.0f / (bottom - top), 0.0f, 0.0f),
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	        vec4( 0.0f,  0.0f,  2.0f / (nearVal - farVal),  0.0f),
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	        vec4((left    + right ) / (left    - right ),
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	             (bottom  + top   ) / (bottom  - top   ),
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	             (nearVal + farVal) / (nearVal - farVal),
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	             1.0f)};
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}
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// Equivalent to calling the above ortho() function with:
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//    ortho(0.0f, width, height, 0.0f, -1.0f, 1.0f)
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// In other words setup an orthographic projection with "natural screen
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// coordinates", (0,0) the top-right corner.
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[[nodiscard]] constexpr mat4 ortho(float width, float height)
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{
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	return {vec4(2.0f / width, 0.0f, 0.0f, 0.0f),
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	        vec4(0.0f, -2.0f / height, 0.0f, 0.0f),
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	        vec4(0.0f, 0.0f, -1.0f, 0.0f),
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	        vec4(-1.0f, 1.0f, 0.0f, 1.0f)};
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}
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// Returns a 4x4 frustum projection matrix. Comparable to
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// the glFrustum() function.
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[[nodiscard]] constexpr mat4 frustum(
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	float left,    float right,
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	float bottom,  float top,
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	float nearVal, float farVal)
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{
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	return {vec4((2.0f * nearVal) / (right - left), 0.0f, 0.0f, 0.0f),
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	        vec4(0.0f, (2.0f * nearVal) / (top - bottom), 0.0f, 0.0f),
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	        vec4((right   + left  ) / (right   - left  ),
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	             (top     + bottom) / (top     - bottom),
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	             (nearVal + farVal) / (nearVal - farVal),
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	             -1.0f),
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	        vec4(0.0f,
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	             0.0f,
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	             (2.0f * farVal * nearVal) / (nearVal - farVal),
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	             0.0f)};
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}
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} // namespace gl
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#endif