The Blitz LightRange() command just modifies the attenuation parameters. The range parameter of a DirectX light is something else. It looks like Blitz by default sets the range parameter to the C++ #defined 'FLT_MAX' i.e. the maximum value that a float can hold. Thats why the lighting is calculated pretty much to infinity. The range parameter of a DirectX light overrules any attenuation curve falloff and all vertices beyond the range receive no lighting calculations at all.If you set the range to a value where the lighting is still visible you get a sharp cutoff of lighting i.e. a black edge around the light.
Here's the DX9 struct for a hardware light.
It has more parameters than the DX7 version but you can see the separate attenuation and range parameters.
typedef struct _D3DLIGHT9 {
D3DLIGHTTYPE Type;
D3DCOLORVALUE Diffuse;
D3DCOLORVALUE Specular;
D3DCOLORVALUE Ambient;
D3DVECTOR Position;
D3DVECTOR Direction;
float Range;
float Falloff;
float Attenuation0;
float Attenuation1;
float Attenuation2;
float Theta;
float Phi;
} D3DLIGHT9;
Members
Type
Type of the light source. This value is one of the members of the D3DLIGHTTYPE enumerated type.
Diffuse
Diffuse color emitted by the light. This member is a D3DCOLORVALUE structure.
Specular
Specular color emitted by the light. This member is a D3DCOLORVALUE structure.
Ambient
Ambient color emitted by the light. This member is a D3DCOLORVALUE structure.
Position
Position of the light in world space, specified by a D3DVECTOR structure. This member has no meaning for directional lights and is ignored in that case.
Direction
Direction that the light is pointing in world space, specified by a D3DVECTOR structure. This member has meaning only for directional and spotlights. This vector need not be normalized, but it should have a nonzero length.
Range
Distance beyond which the light has no effect. The maximum allowable value for this member is the square root of FLT_MAX. This member does not affect directional lights.
Falloff
Decrease in illumination between a spotlight's inner cone (the angle specified by Theta) and the outer edge of the outer cone (the angle specified by Phi).
The effect of falloff on the lighting is subtle. Furthermore, a small performance penalty is incurred by shaping the falloff curve. For these reasons, most developers set this value to 1.0.
Attenuation0
Value specifying how the light intensity changes over distance. Attenuation values are ignored for directional lights. This member represents an attenuation constant. For information about attenuation, see Light Position, Range, and Attenuation. Valid values for this member range from 0.0 to infinity. For non-directional lights, all three attenuation values should not be set to 0.0 at the same time.
Attenuation1
Value specifying how the light intensity changes over distance. Attenuation values are ignored for directional lights. This member represents an attenuation constant. For information about attenuation, see Light Position, Range, and Attenuation. Valid values for this member range from 0.0 to infinity. For non-directional lights, all three attenuation values should not be set to 0.0 at the same time.
Attenuation2
Value specifying how the light intensity changes over distance. Attenuation values are ignored for directional lights. This member represents an attenuation constant. For information about attenuation, see Light Position, Range, and Attenuation. Valid values for this member range from 0.0 to infinity. For non-directional lights, all three attenuation values should not be set to 0.0 at the same time.
Theta
Angle, in radians, of a spotlight's inner conethat is, the fully illuminated spotlight cone. This value must be in the range from 0 through the value specified by Phi.
Phi
Angle, in radians, defining the outer edge of the spotlight's outer cone. Points outside this cone are not lit by the spotlight. This value must be between 0 and pi.
[Edit] OpenGL does not appear to have the equivalent.
Here's the DX9 struct for a hardware light.
It has more parameters than the DX7 version but you can see the separate attenuation and range parameters.
typedef struct _D3DLIGHT9 {
D3DLIGHTTYPE Type;
D3DCOLORVALUE Diffuse;
D3DCOLORVALUE Specular;
D3DCOLORVALUE Ambient;
D3DVECTOR Position;
D3DVECTOR Direction;
float Range;
float Falloff;
float Attenuation0;
float Attenuation1;
float Attenuation2;
float Theta;
float Phi;
} D3DLIGHT9;
Members
Type
Type of the light source. This value is one of the members of the D3DLIGHTTYPE enumerated type.
Diffuse
Diffuse color emitted by the light. This member is a D3DCOLORVALUE structure.
Specular
Specular color emitted by the light. This member is a D3DCOLORVALUE structure.
Ambient
Ambient color emitted by the light. This member is a D3DCOLORVALUE structure.
Position
Position of the light in world space, specified by a D3DVECTOR structure. This member has no meaning for directional lights and is ignored in that case.
Direction
Direction that the light is pointing in world space, specified by a D3DVECTOR structure. This member has meaning only for directional and spotlights. This vector need not be normalized, but it should have a nonzero length.
Range
Distance beyond which the light has no effect. The maximum allowable value for this member is the square root of FLT_MAX. This member does not affect directional lights.
Falloff
Decrease in illumination between a spotlight's inner cone (the angle specified by Theta) and the outer edge of the outer cone (the angle specified by Phi).
The effect of falloff on the lighting is subtle. Furthermore, a small performance penalty is incurred by shaping the falloff curve. For these reasons, most developers set this value to 1.0.
Attenuation0
Value specifying how the light intensity changes over distance. Attenuation values are ignored for directional lights. This member represents an attenuation constant. For information about attenuation, see Light Position, Range, and Attenuation. Valid values for this member range from 0.0 to infinity. For non-directional lights, all three attenuation values should not be set to 0.0 at the same time.
Attenuation1
Value specifying how the light intensity changes over distance. Attenuation values are ignored for directional lights. This member represents an attenuation constant. For information about attenuation, see Light Position, Range, and Attenuation. Valid values for this member range from 0.0 to infinity. For non-directional lights, all three attenuation values should not be set to 0.0 at the same time.
Attenuation2
Value specifying how the light intensity changes over distance. Attenuation values are ignored for directional lights. This member represents an attenuation constant. For information about attenuation, see Light Position, Range, and Attenuation. Valid values for this member range from 0.0 to infinity. For non-directional lights, all three attenuation values should not be set to 0.0 at the same time.
Theta
Angle, in radians, of a spotlight's inner conethat is, the fully illuminated spotlight cone. This value must be in the range from 0 through the value specified by Phi.
Phi
Angle, in radians, defining the outer edge of the spotlight's outer cone. Points outside this cone are not lit by the spotlight. This value must be between 0 and pi.
[Edit] OpenGL does not appear to have the equivalent.